[ldapfeed] Add support for LDAP groups (closes #2528116)
Groups from the LDAP server are imported as CWGourp entities, and in_group relationships are created between existing CWUsers and CWGroups
Unit tests have been refactored a bit, especially ti add helper methods to manage LDAP database.
Experiment with the search bar. Try queries like "card sometextualcontent" or
"card wikiid index" or "345".