(OS-133 Fix) More informative image names

Glance live image names now reflect display names instead of "instance-xxxxx"
The extension for *.gc image was removed, and type changed to "Live-Image"
Disk files still have .#.disk extension, but with updated display name.

Note: locally "instance-xxx" and ".gc" are still used because vms requires it.
Name is converted on upload/download to glance.

Change-Id: I4375d8895b09f5544434bdd1a6099daef0dfd23e
Merge "(OS-133 Fix) More informative image names" into stable/folsom