fix bug, where 'add/remove users' button only appeared if group had 'canBrowseAllUsers' checked. 'add/remove' is always present now, and 'canBrowseAllUsers' only determines who appears in the list of users to add/remove. see LDEV-662
LDEV-662: courseAdminCanAddNewUsers and courseAdminCanBrowseAllUsers are now 1-1 with the 'create new user' and 'add/remove users' buttons. Used to need the canAddNewUsers permission before admin/manager would see the 'add/remove users' button.