MDL-34397 Save extra DB query since 'enablecompletion' is cached
MDL-34397 Removing references to fields course.modinfo, sectioncache
MDL-34397 Remove ref to nonexisting course.modinfo in MNET auth
MDL-34397 Allow user=-1 in get_fast_modinfo()
added db field course.cacherev
Temp
MDL-34397 Do not access deprecated field course.modinfo

rebuild_course_cache() now supports resetting cache for multiple but not all courses