Some re-working of getBoardModerators to accomodate also the return of only the ids + created the function allBoardModerators to get the moderators of all the boards

Signed-off-by: emanuele <emanuele45@gmail.com>
Another bunch of refactoring: board moderators and membergroups

Signed-off-by: emanuele <emanuele45@gmail.com>
Another getGroupModerators

Signed-off-by: emanuele <emanuele45@gmail.com>