Add compression in common capabilities doc
Add compression in common capabilities doc

Compression is a common attribute, so add
the compression capability in common capabilities
doc.

Change-Id: I97ca506c7d6be627079c28191d0fb3ab2470ffed

scality/manila,scality/manila,redhat-openstack/manila,NetApp/manila,NetApp/manila,bswartz/manila,openstack/manila,openstack/manila,jcsp/manila,redhat-openstack/manila,vponomaryov/manila,vponomaryov/manila,jcsp/manila,bswartz/manila