Fix build instructions and formatting in README
Fix build instructions and formatting in README

- Fix manual build command
- Fix formatting of command-line examples, directory names
- Rename 'folder' to 'directory' for consistency
- Update sphinx URL

Partial-bug: #1257725
Change-Id: I078bc5b9c931d4bf4e57c8fe7b335db99cc92c29

django-leonardo/horizon,bac/horizon,orbitfp7/horizon,flochaz/horizon,dan1/horizon-x509,pranavtendolkr/horizon,mandeepdhami/horizon,tsufiev/horizon,noironetworks/horizon,RudoCris/horizon,pranavtendolkr/horizon,kfox1111/horizon,wangxiangyu/horizon,RudoCris/horizon,gerrive/horizon,orbitfp7/horizon,philoniare/horizon,ChameleonCloud/horizon,aaronorosen/horizon-congress,FNST-OpenStack/horizon,yeming233/horizon,endorphinl/horizon,coreycb/horizon,ging/horizon,Solinea/horizon,j4/horizon,mrunge/horizon_lib,watonyweng/horizon,VaneCloud/horizon,openstack/horizon,aaronorosen/horizon-congress,bac/horizon,newrocknj/horizon,Tesora/tesora-horizon,xme1226/horizon,ging/horizon,bigswitch/horizon,bigswitch/horizon,mrunge/horizon,Mirantis/mos-horizon,xinwu/horizon,VaneCloud/horizon,vladryk/horizon,coreycb/horizon,saydulk/horizon,CiscoSystems/avos,izadorozhna/dashboard_integration_tests,blueboxgroup/horizon,dan1/horizon-x509,eayunstack/horizon,django-leonardo/horizon,luhanhan/horizon,luhanhan/horizon,zouyapeng/horizon,Hodorable/0602,philoniare/horizon,dan1/horizon-proto,doug-fish/horizon,bac/horizon,yjxtogo/horizon,FNST-OpenStack/horizon,FNST-OpenStack/horizon,flochaz/horizon,endorphinl/horizon-fork,dan1/horizon-x509,nvoron23/avos,maestro-hybrid-cloud/horizon,CiscoSystems/avos,Daniex/horizon,tqtran7/horizon,tellesnobrega/horizon,j4/horizon,Metaswitch/horizon,orbitfp7/horizon,Tesora/tesora-horizon,NeCTAR-RC/horizon,maestro-hybrid-cloud/horizon,VaneCloud/horizon,liyitest/rr,RudoCris/horizon,Dark-Hacker/horizon,redhat-cip/horizon,wolverineav/horizon,BiznetGIO/horizon,Dark-Hacker/horizon,endorphinl/horizon,ChameleonCloud/horizon,agileblaze/OpenStackTwoFactorAuthentication,takeshineshiro/horizon,CiscoSystems/avos,Tesora/tesora-horizon,tellesnobrega/horizon,mandeepdhami/horizon,karthik-suresh/horizon,tsufiev/horizon,nvoron23/avos,Metaswitch/horizon,sandvine/horizon,gerrive/horizon,froyobin/horizon,j4/horizon,Daniex/horizon,tellesnobrega/horizon,agileblaze/OpenStackTwoFactorAuthentication,pranavtendolkr/horizon,xinwu/horizon,izadorozhna/dashboard_integration_tests,yeming233/horizon,BiznetGIO/horizon,JioCloud/horizon,noironetworks/horizon,idjaw/horizon,Tesora/tesora-horizon,mdavid/horizon,anthonydillon/horizon,CiscoSystems/avos,davidcusatis/horizon,tsufiev/horizon,flochaz/horizon,promptworks/horizon,karthik-suresh/horizon,idjaw/horizon,redhat-openstack/horizon,Mirantis/mos-horizon,damien-dg/horizon,newrocknj/horizon,davidcusatis/horizon,karthik-suresh/horizon,redhat-cip/horizon,nvoron23/avos,FNST-OpenStack/horizon,wangxiangyu/horizon,agileblaze/OpenStackTwoFactorAuthentication,damien-dg/horizon,zouyapeng/horizon,tqtran7/horizon,karthik-suresh/horizon,sandvine/horizon,philoniare/horizon,bigswitch/horizon,blueboxgroup/horizon,mdavid/horizon,Hodorable/0602,vladryk/horizon,coreycb/horizon,xinwu/horizon,eayunstack/horizon,noironetworks/horizon,luhanhan/horizon,pranavtendolkr/horizon,eayunstack/horizon,henaras/horizon,watonyweng/horizon,wangxiangyu/horizon,davidcusatis/horizon,dan1/horizon-proto,Solinea/horizon,damien-dg/horizon,mdavid/horizon,vladryk/horizon,philoniare/horizon,NeCTAR-RC/horizon,endorphinl/horizon,mrunge/openstack_horizon,NeCTAR-RC/horizon,promptworks/horizon,Solinea/horizon,CiscoSystems/horizon,Hodorable/0602,openstack/horizon,bigswitch/horizon,nvoron23/avos,blueboxgroup/horizon,orbitfp7/horizon,liyitest/rr,openstack/horizon,maestro-hybrid-cloud/horizon,gerrive/horizon,anthonydillon/horizon,coreycb/horizon,yjxtogo/horizon,NCI-Cloud/horizon,tqtran7/horizon,luhanhan/horizon,Mirantis/mos-horizon,endorphinl/horizon-fork,redhat-openstack/horizon,takeshineshiro/horizon,redhat-openstack/horizon,yjxtogo/horizon,icloudrnd/automation_tools,davidcusatis/horizon,henaras/horizon,takeshineshiro/horizon,Dark-Hacker/horizon,Dark-Hacker/horizon,flochaz/horizon,dan1/horizon-x509,mdavid/horizon,maestro-hybrid-cloud/horizon,VaneCloud/horizon,endorphinl/horizon-fork,Hodorable/0602,froyobin/horizon,RudoCris/horizon,kfox1111/horizon,watonyweng/horizon,mrunge/horizon_lib,anthonydillon/horizon,doug-fish/horizon,sandvine/horizon,Metaswitch/horizon,CiscoSystems/horizon,saydulk/horizon,mandeepdhami/horizon,zouyapeng/horizon,froyobin/horizon,kfox1111/horizon,noironetworks/horizon,redhat-cip/horizon,aaronorosen/horizon-congress,newrocknj/horizon,saydulk/horizon,newrocknj/horizon,xme1226/horizon,ChameleonCloud/horizon,sandvine/horizon,Mirantis/mos-horizon,redhat-cip/horizon,redhat-openstack/horizon,BiznetGIO/horizon,watonyweng/horizon,promptworks/horizon,zouyapeng/horizon,django-leonardo/horizon,henaras/horizon,mrunge/horizon,wolverineav/horizon,mrunge/openstack_horizon,bac/horizon,tsufiev/horizon,Daniex/horizon,icloudrnd/automation_tools,idjaw/horizon,kfox1111/horizon,endorphinl/horizon,liyitest/rr,mandeepdhami/horizon,ging/horizon,tellesnobrega/horizon,tqtran7/horizon,agileblaze/OpenStackTwoFactorAuthentication,takeshineshiro/horizon,BiznetGIO/horizon,anthonydillon/horizon,Solinea/horizon,openstack/horizon,dan1/horizon-proto,JioCloud/horizon,CiscoSystems/horizon,xme1226/horizon,Metaswitch/horizon,wolverineav/horizon,mrunge/horizon,blueboxgroup/horizon,mrunge/openstack_horizon,Daniex/horizon,wolverineav/horizon,NCI-Cloud/horizon,NeCTAR-RC/horizon,mrunge/horizon_lib,JioCloud/horizon,dan1/horizon-proto,damien-dg/horizon,yeming233/horizon,doug-fish/horizon,NCI-Cloud/horizon,saydulk/horizon,ging/horizon,CiscoSystems/horizon,yjxtogo/horizon,j4/horizon,doug-fish/horizon,ChameleonCloud/horizon,promptworks/horizon,endorphinl/horizon-fork,xinwu/horizon,icloudrnd/automation_tools,idjaw/horizon,vladryk/horizon,liyitest/rr,henaras/horizon,django-leonardo/horizon,gerrive/horizon,yeming233/horizon,icloudrnd/automation_tools,wangxiangyu/horizon,NCI-Cloud/horizon