enable applications to specify OF versions
enable applications to specify OF versions

Some applications need to use particular OF versions.

With this patch, applications can specify OF versions in the following
way:

class YourApplication(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_1.OFP_VERSION, ofproto_v1_2.OFP_VERSION]

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>
Reviewed-by: Isaku Yamahata <4b3abd66323411eeceff090ab3754dd766fc4b25@valinux.co.jp>

evanscottgray/ryu,castroflavio/ryu,zangree/ryu,John-Lin/ryu,haniehrajabi/ryu,ttsubo/ryu,yamada-h/ryu,lagopus/ryu-lagopus-ext,yamt/ryu,sivaramakrishnansr/ryu,lsqtongxin/ryu,StephenKing/summerschool-2015-ryu,diogommartins/ryu,osrg/ryu,sivaramakrishnansr/ryu,ysywh/ryu,fkakuma/ryu,darjus-amzn/ryu,OpenState-SDN/ryu,alyosha1879/ryu,pichuang/ryu,lzppp/mylearning,samrussell/ryu,Tejas-Subramanya/RYU_MEC,pichuang/ryu,zangree/ryu,elahejalalpour/ELRyu,yamt/ryu,umkcdcrg01/ryu_openflow,OpenState-SDN/ryu,iwaseyusuke/ryu,hisaharu/ryu,StephenKing/ryu,alanquillin/ryu,torufuru/oolhackathon,pichuang/ryu,gareging/SDN_Framework,fujita/ryu,StephenKing/ryu,sivaramakrishnansr/ryu,evanscottgray/ryu,fkakuma/ryu,lsqtongxin/ryu,yamt/ryu,habibiefaried/ryu,jalilm/ryu,muzixing/ryu,samrussell/ryu,fujita/ryu,elahejalalpour/ELRyu,darjus-amzn/ryu,John-Lin/ryu,jalilm/ryu,gareging/SDN_Framework,torufuru/oolhackathon,osrg/ryu,darjus-amzn/ryu,openvapour/ryu,fujita/ryu,fujita/ryu,zyq001/ryu,alyosha1879/ryu,Tejas-Subramanya/RYU_MEC,openvapour/ryu,shinpeimuraoka/ryu,gopchandani/ryu,osrg/ryu,iwaseyusuke/ryu,StephenKing/ryu,StephenKing/ryu,ntts-clo/ryu,TakeshiTseng/ryu,evanscottgray/ryu,iwaseyusuke/ryu,umkcdcrg01/ryu_openflow,jkoelker/ryu,John-Lin/ryu,gopchandani/ryu,citrix-openstack-build/ryu,iwaseyusuke/ryu,jalilm/ryu,Tejas-Subramanya/RYU_MEC,yamt/ryu,shinpeimuraoka/ryu,TakeshiTseng/ryu,zangree/ryu,osrg/ryu,zangree/ryu,diogommartins/ryu,Tesi-Luca-Davide/ryu,torufuru/OFPatchPanel,ttsubo/ryu,takahashiminoru/ryu,o3project/ryu-oe,pichuang/ryu,lsqtongxin/ryu,habibiefaried/ryu,Zouyiran/ryu,alanquillin/ryu,StephenKing/ryu,umkcdcrg01/ryu_openflow,mikhaelharswanto/ryu,habibiefaried/ryu,openvapour/ryu,fkakuma/ryu,ynkjm/ryu,lagopus/ryu-lagopus-ext,habibiefaried/ryu,sivaramakrishnansr/ryu,Zouyiran/ryu,ntts-clo/ryu,citrix-openstack/build-ryu,umkcdcrg01/ryu_openflow,Tejas-Subramanya/RYU_MEC,torufuru/OFPatchPanel,alanquillin/ryu,habibiefaried/ryu,jalilm/ryu,takahashiminoru/ryu,fkakuma/ryu,gareging/SDN_Framework,ysywh/ryu,TakeshiTseng/ryu,castroflavio/ryu,Zouyiran/ryu,ynkjm/ryu,citrix-openstack-build/ryu,alyosha1879/ryu,muzixing/ryu,ntts-clo/mld-ryu,zyq001/ryu,torufuru/oolhackathon,Tejas-Subramanya/RYU_MEC,sivaramakrishnansr/ryu,lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext,Tesi-Luca-Davide/ryu,zyq001/ryu,alanquillin/ryu,Tesi-Luca-Davide/ryu,haniehrajabi/ryu,OpenState-SDN/ryu,ynkjm/ryu,darjus-amzn/ryu,zyq001/ryu,takahashiminoru/ryu,ttsubo/ryu,jkoelker/ryu,gareging/SDN_Framework,lagopus/ryu-lagopus-ext,muzixing/ryu,haniehrajabi/ryu,shinpeimuraoka/ryu,unifycore/ryu,osrg/ryu,OpenState-SDN/ryu,fujita/ryu,diogommartins/ryu,ysywh/ryu,StephenKing/summerschool-2015-ryu,lzppp/mylearning,ttsubo/ryu,ysywh/ryu,citrix-openstack/build-ryu,gopchandani/ryu,gopchandani/ryu,alanquillin/ryu,StephenKing/summerschool-2015-ryu,ynkjm/ryu,Tesi-Luca-Davide/ryu,muzixing/ryu,mikhaelharswanto/ryu,zyq001/ryu,pichuang/ryu,openvapour/ryu,StephenKing/summerschool-2015-ryu,TakeshiTseng/ryu,alyosha1879/ryu,shinpeimuraoka/ryu,gareging/SDN_Framework,hisaharu/ryu,muzixing/ryu,gopchandani/ryu,takahashiminoru/ryu,Zouyiran/ryu,haniehrajabi/ryu,ynkjm/ryu,yamt/ryu,umkcdcrg01/ryu_openflow,openvapour/ryu,iwaseyusuke/ryu,hisaharu/ryu,ntts-clo/mld-ryu,diogommartins/ryu,elahejalalpour/ELRyu,hisaharu/ryu,John-Lin/ryu,darjus-amzn/ryu,ykaneko/ryu,jazzmes/ryu,John-Lin/ryu,ttsubo/ryu,ysywh/ryu,zangree/ryu,fkakuma/ryu,jkoelker/ryu,StephenKing/summerschool-2015-ryu,diogommartins/ryu,Tesi-Luca-Davide/ryu,jazzmes/ryu,lzppp/mylearning,shinpeimuraoka/ryu,lzppp/mylearning,haniehrajabi/ryu,hisaharu/ryu,castroflavio/ryu,OpenState-SDN/ryu,elahejalalpour/ELRyu,lzppp/mylearning,takahashiminoru/ryu,jazzmes/ryu,jalilm/ryu,TakeshiTseng/ryu,elahejalalpour/ELRyu,ykaneko/ryu,lsqtongxin/ryu,Zouyiran/ryu,yamada-h/ryu,o3project/ryu-oe,lsqtongxin/ryu,unifycore/ryu