Admin move to group 12305

This fixes the list of Groups available for an Admin when they right-click and "Move to Group". Now we only show the groups that the Admin is a member of.

This is a partial fix for http://trac.openmicroscopy.org.uk/ome/ticket/12305

To test, log in as Admin, right click on Dataset or Image -> Move to Group.
List of groups should only be the ones that the Admin is a member of.