added db field course.cacherev
some comments
MDL-34397 Move course content cache to MUC
Temp
MDL-34397 Removing references to course.modinfo
reset cacherev and not modinfo
course overview retrieve cacherev
MDL-34397 Removing references to fields course.modinfo, sectioncache
MDL-34397 Save extra DB query since 'enablecompletion' is cached
MDL-34397 Remove ref to nonexisting course.modinfo in MNET auth
MDL-34397 Allow user=-1 in get_fast_modinfo()