restore search detail selector hack in LdapGroupPersistence, fix deleteGroup so it properly clears members

small tweaks and fixes to get integration tests to pass; removed support for querying for other user memberships in GMSClient API

ac2 - Changed thread safety in LdapPersistence.  Removed the returning of groups from the add and modify group persistence APIs

added GroupDetailSelector so GroupPersistence implementation can configure whether group details should be returned from searches

Story ac2 rework. Removed getUserGroups() from the API since we already have getGroups(). This also stops us from exposing com.unboundid.ldap.sdk.DN to the API.