add 'pivot' lookup type, add handling for grouplist (via pivot) lookup and marshal and key extract functions.
Normal 'group' lookup functions take an identifier for a group (id or name) and return a group entry.
The getgrouplist(3) call dispatches to the NS method 'getgroupmembersip', which is given the name of a USER, and returns a list of GIDs. This is a unique access method to the group(5) database that does not have an analog in the other entity databases, it corresponds mostly like a 'pivot table'. Where a regular query is 'given a row id, give me a set of columns', this is 'given a column (a member of group), give me the rows that match'