MDL-37973 gradebook Return a maxgrade of '-' if grade type is TEXT

Including tests for correct return from
grade_edit_tree_column_range->get_item_cell()
MDL-41227 core_course:fixed up some JS that was confusing activity visibility
MDL-41885 lib: Introduce component_callback_exists

Determines if a callback in a module exists without needing to
call that callback.
MDL-40050 webservice: Replace add_to_log() with new events
MDL-41848 SCORM: Drag drop SCORM upload fix
MDL-41954 Fix the grade for assessment calculation in the Workshop module

In a pretty rare case of zero variance of received assessments, the "distance"
of the evaluated assessment from the referential ("best") one was not increased
regardless it's actual value. This led to higher grades for assessments in
certain situations (see the tracker for a particular example).
MDL-41885 modules now declare use of question bank

* FEATURE_USES_QUESTION_BANK is now a module_supports flag which declares
  that an activity uses the question engine.

* question_module_uses_questions can be used to determine if a module
  uses the question bank.
MDL-12403 backup: Ability to exclude question bank

Now users can choose to exclude the question bank from the backup,
this will in turn prevent any modules which use the question bank
from being included in the backup.
MDL-12403 backup: configure question bank in automated backups
MDL-12403 backup: ability configure default for question bank excludes
MDL-12403 backup: prevent unset config from being applied
MDL-26408 enrol_imsenterprise: fix invalid component
MDL-33416 files: Remove unused reference fields in files table

Fields files.referencelastsync and files.referencelifetime just waste the space and actually duplicate the fields
files_reference.lifetime and files_reference.lastsync
MDL-41888 separate out quiz statistics calculations from report code

also code clean up.
MDL-41888 allow for a blank string as format to mean not to show stat

as in MDL-41929 which applies to older stable branches.
MDL-41888 More comments
MDL-32773 Add a help icon for button 'Set main file' in filemanager
MDL-41676 Corrected logic when to dim the activity name and content
MDL-41176 fix obvious bugs and typos in new user API
MDL-41176 make sure fresh full user record is used when mailing email confirmation