This commit coverts everything in the codebase to use the new
users_order_by_sql function when sorting lists of users. More details in
the bug.
Note that this does not change places where users are displayed in a
sortable table, and the sort order comes from the table.
* Display the grouping a course module belongs to on the course page - for course managers only.
* When adding users to groups, display the groups a user already belongs to.
* Added an overview report that shows groupings, groups and members for a course.
* Added a dialogue to automatically create groups and assign members based on either the number of desired groups or the number of desired users per group.