Function saveCourseAndSync

Save a course, then — when lessons were added, removed or reordered, or their rules changed — open lessons to clients who should now have them. Pass the course as it was loaded (previous) so an edit that touches no rules (a renamed lesson, a new description) doesn't reload every enrollment. onSaved is called with the saved course before lessons are opened, so a failure while opening them (which rejects) doesn't hide that the course was saved.