Document autoscaling resource properties
Document autoscaling resource properties

Adds descriptions to the properties of:
* AWS::AutoScaling::LaunchConfiguration
* AWS::AutoScaling::AutoScalingGroup
* AWS::AutoScaling::ScalingPolicy
* OS::Heat::InstanceGroup
and wraps attribute descriptions with gettext _(

Change-Id: Ie825c2b122a6c2ce8ff83f9beb9f98487aaa8d54
Closes-Bug: #1224131

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