heat cli: encapsulate template arg-parsing
heat cli: encapsulate template arg-parsing

Encapsulate template argument parsing in a helper function
cleans up some duplication and provides a single place to add
swift-template-url logic

Ref #216

Change-Id: I36515f318ed79899a2710899ffca83e4452c61f4
Signed-off-by: Steven Hardy <4d1810d1ff6d7f22d774341c4549c02173d2f2ab@redhat.com>

dragorosson/heat,ntt-sic/heat,cwolferh/heat-scratch,jasondunsmore/heat,citrix-openstack-build/heat,maestro-hybrid-cloud/heat,Triv90/Heat,gonzolino/heat,dragorosson/heat,jasondunsmore/heat,gonzolino/heat,steveb/heat,cryptickp/heat,pshchelo/heat,openstack/heat,redhat-openstack/heat,srznew/heat,noironetworks/heat,takeshineshiro/heat,JioCloud/heat,rickerc/heat_audit,NeCTAR-RC/heat,dims/heat,rickerc/heat_audit,pratikmallya/heat,dims/heat,NeCTAR-RC/heat,ntt-sic/heat,rdo-management/heat,rdo-management/heat,rh-s/heat,Triv90/Heat,pshchelo/heat,citrix-openstack-build/heat,steveb/heat,Triv90/Heat,JioCloud/heat,maestro-hybrid-cloud/heat,varunarya10/heat,varunarya10/heat,miguelgrinberg/heat,takeshineshiro/heat,rh-s/heat,miguelgrinberg/heat,redhat-openstack/heat,cryptickp/heat,noironetworks/heat,cwolferh/heat-scratch,openstack/heat,pratikmallya/heat,srznew/heat