Move volume snapshots table to volumes panel

Now that instance snapshots are just images, the images & snapshots
page only has images and volume snapshots. This is an odd combination.
I think we should now move volume snapshots to the volumes panel,
since a volume snapshot is tied to a volume.

Closes-Bug: #1190843
Change-Id: I3e12cec8b859a30db9f131e9889a92277e064086
Fix a code indentation error

Change-Id: I010946cfebf159bd888e0a3a9ebb46e02d223036
Enforce FlavorExtraSpecs Key format

When creating a key name with characters like '/' that are not
being encoded or cannot be handled as expected by routes when
matching the url, then it's not possible to remove them anymore.
The new format apply the restriction: r"^[\w\.\-: ]+$"

Change-Id: Ie6f982a0e44212bf0d58da66b89aff7740d06e8f
Closes-Bug: #1256119
Merge "Move volume snapshots table to volumes panel"
Merge "Fix a code indentation error"
Merge "Enforce FlavorExtraSpecs Key format"