Update kgcreatesuperuser command:

*  Allow creating new institutes, always.  Without this, not possible to
   test that we can create a new institute if
   institutes already exist.

*  Validate institute name is a valid group name.

*  Create a group, if required.

Change-Id: Ie0ff38c01d38e32a44dc6b3bb6711c2fdbae462d