image spec: Correct set of acceptable characters in tags
image spec: Correct set of acceptable characters in tags

The image spec did not match the regexp that validates tags. It
neglected to mention that period and dash characters are allowed in
tags, as long as they are not the first character. It also did not
mention the length limit for tags.

Signed-off-by: Aaron Lehmann <8ecfc6017a87905413dcd7d63696a2a4c351b604@docker.com>

justincormack/docker,imkin/moby,erikh/docker,x1022as/docker,lixiaobing10051267/docker,darrenstahlmsft/docker,tagomoris/docker,hqhq/moby,charleszheng44/moby,thtanaka/docker,Syntaxide/docker,mikedougherty/docker,portworx/docker,ColinHebert/docker,jimjag/docker,jameszhan/docker,tklauser/docker,dmcgowan/docker,flavio/docker,lixiaobing10051267/docker,ajaymdesai/docker,djs55/docker,moypray/docker,charleszheng44/moby,dperny/docker,yongtang/docker,jhorwit2/docker,harche/docker,kolyshkin/moby,13W/docker,haveatry/docker,yongtang/docker,yosifkit/docker,noironetworks/docker,gjaskiewicz/moby,tophj-ibm/moby,whuwxl/docker,diogomonica/docker,fcrisciani/docker,tianon/docker,msabansal/docker,tophj-ibm/docker,stevvooe/docker,Mokolea/docker,moypray/docker,endophage/docker,kolyshkin/docker,mstanleyjones/docker,PatrickLang/moby,dongjoon-hyun/docker,prertik/docker,gschaetz/moby,cloudflare/docker,liaoqingwei/docker,projectatomic/docker,jwhonce/docker,michelvocks/docker,sfsmithcha/docker,jwhonce/docker,jlhawn/docker,gschaetz/moby,HideoYamauchi/docker,icaoweiwei/docker,coolljt0725/docker,HideoYamauchi/docker,tonistiigi/docker,djs55/docker,rremer/moby,laijs/moby,madhanrm/docker,mtrmac/docker,srust/docker,jhorwit2/docker,yasiramin10p/moby,mahak/docker,xiekeyang/docker,estesp/docker,xiaods/docker,containers/storage,darrenstahlmsft/docker,flavio/docker,abhinavdahiya/docker,13W/docker,cloudflare/docker,paralin/docker,ibuildthecloud/docker,rancher/docker,johnstep/moby-moby,ajaymdesai/docker,djs55/docker,crosbymichael/docker,mahak/docker,kunalkushwaha/docker,KarthikNayak/docker,tophj-ibm/moby,nawawi/docker,sterchelen/docker,duglin/docker,13W/docker,13W/docker,eskaaren/docker,mkumatag/docker,moby/moby,xuxinkun/docker,ibuildthecloud/docker,moul/docker,ColinHebert/docker,KingEmet/docker,HuKeping/docker,nawawi/docker,dmcgowan/docker,unclejack/docker,rremer/moby,abhinavdahiya/docker,ibuildthecloud/docker,duglin/docker,Syntaxide/docker,vdemeester/docker,darrenstahlmsft/moby,nalind/docker,laijs/docker,AkihiroSuda/docker,raja-sami-10p/moby,yummypeng/docker,hypriot/docker,JMesser81/docker,akira-baruah/docker,cpuguy83/docker,justyntemme/docker,konstruktoid/docker-1,endophage/docker,kolyshkin/moby,cloudflare/docker,laijs/docker,kencochrane/docker,akira-baruah/docker,brahmaroutu/docker,liaoqingwei/docker,mtesselH/docker,yummypeng/docker,bonczj/moby-json-file-logger,dperny/docker,catinthesky/docker,cpuguy83/docker,dgageot/docker,mtesselH/docker,ndeloof/docker,hypriot/docker,splunk/docker,sdurrheimer/docker,gnailuy/docker,POLJM242/docker,zhuguihua/docker,nalind/docker,allencloud/docker,mike1729/docker,JMesser81/docker,bluebreezecf/docker,rhatdan/docker,allencloud/docker,lixiaobing1/docker,msabansal/docker,Ramzec/docker,kencochrane/docker,KarthikNayak/docker,mtanlee/docker,dgageot/docker,Mokolea/docker,diogomonica/docker,asbjornenge/docker,charleszheng44/moby,ndeloof/docker,gnailuy/docker,mikebrow/docker,prertik/docker,ripcurld0/moby,ndeloof/docker,shishir-a412ed/docker,coolljt0725/docker,bearstech/moby,jlhawn/docker,gnailuy/docker,darrenstahlmsft/moby,Mokolea/docker,eskaaren/docker,mixja/docker,lixiaobing1/docker,maxamillion/docker,rhatdan/docker,nawawi/docker,jlebon/docker,trebonian/docker,mike1729/docker,miminar/docker,johnstep/moby-moby,Ramzec/docker,maxamillion/docker,tophj-ibm/docker,justincormack/docker,msabansal/docker,moul/docker,shishir-a412ed/docker,asbjornenge/docker,AkihiroSuda/docker,ripcurld0/moby,danyalKhaliq10p/moby,splunk/docker,nawawi/docker,projectatomic/docker,dsheets/moby,mahak/docker,hypriot/docker,ibuildthecloud/docker,thaJeztah/docker,AkihiroSuda/docker,xuxinkun/docker,dims/docker,sterchelen/docker,rhatdan/docker,KarthikNayak/docker,sarnautov/moby,shhsu/docker,ajaymdesai/docker,moby/moby,HideoYamauchi/docker,brahmaroutu/docker,docker/docker,PatrickLang/moby,dims/docker,xiekeyang/docker,docker/docker,sarnautov/moby,kolyshkin/docker,qudongfang/docker,laijs/moby,danyalKhaliq10p/moby,dccurtis/docker,mikedougherty/docker,asbjornenge/docker,sdurrheimer/docker,ffoysal/docker,tianon/docker,harche/docker,yosifkit/docker,twaugh/docker,pradipd/moby,pradipd/moby,Syntaxide/docker,x1022as/docker,splunk/docker,miminar/docker,ffoysal/docker,thtanaka/docker,justyntemme/docker,pramodhkp/moby,gjaskiewicz/moby,jvanz/docker,dongjoon-hyun/docker,dongjoon-hyun/docker,mstanleyjones/docker,mtesselH/docker,crosbymichael/docker,xiekeyang/docker,jvanz/docker,scotttlin/docker,tmp6154/docker,dmcgowan/docker,q384566678/docker,kunalkushwaha/docker,yp-engineering/docker,eskaaren/docker,hqhq/moby,yongtang/docker,rhatdan/storage,dsau/docker,dsau/docker,thaJeztah/docker,rremer/moby,yp-engineering/docker,mikebrow/docker,srust/docker,mstanleyjones/docker,dsheets/moby,stevvooe/docker,bonczj/moby-json-file-logger,jameszhan/docker,unclejack/docker,afein/docker,YuPengZTE/docker,13W/docker,ffoysal/docker,dccurtis/docker,tmp6154/docker,coolljt0725/docker,allencloud/docker,xuxinkun/docker,trebonian/docker,trebonian/docker,bearstech/moby,pradipd/moby,michael-holzheu/docker,moul/docker,bluebreezecf/docker,harche/docker,catinthesky/docker,tonistiigi/docker,thaJeztah/docker,erikstmartin/docker,estesp/docker,moby/moby,yosifkit/docker,amatsus/docker,afein/docker,sdurrheimer/docker,dims/docker,danyalKhaliq10p/moby,HuKeping/docker,justincormack/docker,dsau/docker,mixja/docker,afein/docker,thtanaka/docker,jimjag/docker,moypray/docker,resin-io/docker,pramodhkp/moby,hqhq/moby,scotttlin/docker,AkihiroSuda/docker,tklauser/docker,containers/storage,flavio/docker,lixiaobing1/docker,Mokolea/docker,darrenstahlmsft/docker,srust/docker,sfsmithcha/docker,shhsu/docker,KingEmet/docker,dgageot/docker,gnailuy/docker,raja-sami-10p/moby,alfred-landrum/docker,icaoweiwei/docker,dperny/docker,fcrisciani/docker,mohmost12/docker,prertik/docker,diogomonica/docker,jhorwit2/docker,xiaods/docker,shhsu/docker,tagomoris/docker,mohmost12/docker,vdemeester/docker,YuPengZTE/docker,catinthesky/docker,portworx/docker,konstruktoid/docker-1,naveed-jamil-tenpearls/moby,tonistiigi/docker,rancher/docker,johnstep/moby-moby,docker/docker,kunalkushwaha/docker,ibuildthecloud/docker,cpuguy83/docker,flavio/docker,SvenDowideit/docker,SvenDowideit/docker,mixja/docker,coreos/docker,unclejack/docker,liaoqingwei/docker,erikstmartin/docker,alfred-landrum/docker,mkumatag/docker,lixiaobing10051267/docker,madhanrm/docker,kojiromike/docker,gschaetz/moby,madhanrm/docker,portworx/docker,raja-sami-10p/moby,tophj-ibm/docker,jlebon/docker,whuwxl/docker,haveatry/docker,dccurtis/docker,mtrmac/docker,jwhonce/docker,q384566678/docker,sfsmithcha/docker,jlebon/docker,crosbymichael/docker,rhatdan/storage,xiaods/docker,jlhawn/docker,duglin/docker,PatrickLang/moby,coreos/docker,estesp/docker,trebonian/docker,zhuguihua/docker,amatsus/docker,naveed-jamil-tenpearls/moby,noironetworks/docker,bearstech/moby,JMesser81/docker,thaJeztah/docker,laijs/moby,michael-holzheu/docker,erikstmartin/docker,erikh/docker,mohmost12/docker,mtrmac/docker,laijs/docker,kojiromike/docker,nalind/docker,rancher/docker,projectatomic/docker,cpuguy83/docker,paralin/docker,Ramzec/docker,jthelin/docker,sterchelen/docker,stevvooe/docker,cyphar/docker,darrenstahlmsft/moby,kolyshkin/moby,POLJM242/docker,yosifkit/docker,brahmaroutu/docker,mikedougherty/docker,bluebreezecf/docker,coreos/docker,qudongfang/docker,konstruktoid/docker-1,sarnautov/moby,mikebrow/docker,michelvocks/docker,qudongfang/docker,jimjag/docker,jvanz/docker,endophage/docker,jameszhan/docker,bearstech/moby,bonczj/moby-json-file-logger,shishir-a412ed/docker,zhuguihua/docker,haveatry/docker,mike1729/docker,abhinavdahiya/docker,moby/moby,icaoweiwei/docker,paralin/docker,rhatdan/storage,Ramzec/docker,yasiramin10p/moby,mahak/docker,jthelin/docker,mtanlee/docker,imkin/moby,HuKeping/docker,konstruktoid/docker-upstream,konstruktoid/docker-upstream,ripcurld0/moby,tmp6154/docker,amatsus/docker,containers/storage,x1022as/docker,alfred-landrum/docker,pramodhkp/moby,fcrisciani/docker,justyntemme/docker,cyphar/docker,tagomoris/docker,kojiromike/docker,tklauser/docker,vdemeester/docker,michelvocks/docker,resin-io/docker,michael-holzheu/docker,paralin/docker,cyphar/docker,KingEmet/docker,nalind/docker,mtanlee/docker,erikh/docker,yasiramin10p/moby,scotttlin/docker,gjaskiewicz/moby,konstruktoid/docker-upstream,mkumatag/docker,yummypeng/docker,imkin/moby,moul/docker,maxamillion/docker,noironetworks/docker,whuwxl/docker,tophj-ibm/moby,miminar/docker,kencochrane/docker,YuPengZTE/docker,q384566678/docker,jimjag/docker,ColinHebert/docker,naveed-jamil-tenpearls/moby,resin-io/docker,konstruktoid/docker-upstream,twaugh/docker,twaugh/docker,dsheets/moby,SvenDowideit/docker,yp-engineering/docker