[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.

fontcolor = 'black'
bgcolor = '#FFFFFF'
stylesheets = sheet['stylesheets'] + ['%s/mycube.css' % datadir_url]