SAK-25948 Don't allow duplicate joinable set names


git-svn-id: https://source.sakaiproject.org/svn/site-manage/branches/sakai-10.x@307555 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-25965 Edit Joinable Groups page: Sort groups alphabetically	


git-svn-id: https://source.sakaiproject.org/svn/site-manage/branches/sakai-10.x@307556 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-25967 Joinable Groups: Standardize auto-generated group naming convention


git-svn-id: https://source.sakaiproject.org/svn/site-manage/branches/sakai-10.x@307557 66ffb92e-73f9-0310-93c1-f5514f145a0a