Document glance v2 commands

The glance v2 commands need to be called as:
glance -os-image-api-version 2 CMD

Implement logic for this and enhance output.
Closes-Bug: #1367430

Change-Id: Ibc81d49494a203c9c8f469a2a0f93e4c1786af7e
Merge "Document glance v2 commands"