changes for group::get: make array optional return dict of values which can be more easily passed around remove unneeded code (flushing of get_title from memoize cache, but function does not exist remove redundant SQL code in group::delete rCVS: ----------------------------------------------------------------------
move caching of group memberships from util_memoize cache into separate, partitioned cache (group_cache) to reduce stress on util_memoize and improve scalability