Fix broken SQL query.
Query to retrieve the nid of the latest modelversion node referred
to the old integer field 'field_modelversion_modelnid' and hadn't
been updated to the Node Reference field used in te 7.x version
of the Model Library. Missed during the migration to D7.
Fixing email messaging.
Some calls to the messaging function were sending the wrong
arguments, specifically during the migration to Drupal 7, the
messaging function had to be changed from accepting the recipient's
uid to their email address. Lingering calls were still sending
uids.
Adding system enable/disable setting.
Adding toggle to enable/disable for the Model Review system. This
will also require some changes to the Model Library templates to
only display Model Review elements when the system is enabled.