Support for resizing a trove instance

Added menu item and dialog to allow the
user to select a new flavor for their
trove instance

Change-Id: I5ef42067887e1f1f1f5ee3224df7b6391be0a375
Implements: blueprint trove-resize-instance-dialog
Merge "Support for resizing a trove instance"
Merge branch 'master' of https://github.com/openstack/horizon