cache stage 1 - allow multiple resets
MDL-34397 Removing references to course.modinfo
MDL-34397 Do not access deprecated field course.modinfo

rebuild_course_cache() now supports resetting cache for multiple but not all courses
MDL-34397 TODO
changes to rebuild_course_cache() merge with cache
section_info
course_modinfo (after sectioninfo)
MDL-34397 Object section_info calculates expensive data on demand only
MDL-34397 dont write to cm_info properties
MDL-34397 (other issue?) function moveto_module does not modify properties of object
MDL-34397 do not write to cm_info properties
MDL-34397 Properties of cm_info are read-only and calculated on request
cm_info
useful: added cachecreated
useful change to course_modinfo
useful changes in section_info
MDL-34397 remove  arg from seciton_info as not needed
useful change to course_modinfo (store cachecreated)
course modinfo caching, stage 1
course modinfo caching stage 1 minus