ADD single group selector functions

git-svn-id: http://svn.montala.net/svn/resourcespace@5814 c08608d7-6e46-0410-86ca-f2a6f1370df5
ADD limit_to option to api_search, to limit results to a single field

git-svn-id: http://svn.montala.net/svn/resourcespace@5815 c08608d7-6e46-0410-86ca-f2a6f1370df5
CHG when plugins are initialized, make sure that hooks are only included once (to support system logins)

git-svn-id: http://svn.montala.net/svn/resourcespace@5816 c08608d7-6e46-0410-86ca-f2a6f1370df5