MDL-34363 gradebook Adding check to prevent incorrect override when a blank feedback is submitted.
MDL-33857 Increase performance of queries for Server files repository

- file_info class now has new methods get_non_empty_children and count_non_empty_children; added default implementation;
- all core classes extending file_info have their implementation of those methods;
- class repository_local_file used for caching get_children() results is removed;
- class repository_local rewritten to use new methods from file_info;
- added caching of retrieved modules in file_browser::get_file_info_context_module() - this query is slow and executed multiple times on big servers
MDL-33857 Increase performance of queries for Server files repository (small improvements)
MDL-35198 replace key_exists by array_key_exists
MDL-28235 form: Help button popup close accessibility improved

AMOS BEGIN
 CPY [close,editor],[close,form]
AMOS END
MDL-28235 form: Removed close icon of help icon popups
MDL-27309 Blocks: command node is taken from dockitem during restore
MDL-32218 Blocks: allowblockstodock is also checked for region dock status
MDL-34228 Completion: Add capability that controls if a user is shown in reports
MDL-32184 - Course - Fixing incorrect redirect when toggling course edit while inside an activity -- Patch provided by Kanika Goyal
MDL-32326 dock: Clarified use of CSS rotation
MDL-35661 local plugins do not have general settings URL
MDL-30691 Adminstration: Added css to break long word in filter table
MDL-35787 Mnet: fixed php strict standards warnings
MDL-35787 Mnet: If student role is not defined then throw error
MDL-35581 lib: Help popups misaligned for right-to-left languages
MDL-31010 comments: setup_course should update  if passed courseid is different from the cached one
MDL-28965 administration: Updating description string for the setting navshowallcourses
MDL-33815 Online Users block: Add query condition to filter out deleted users and lastaccess date greater than now
MDL-21801 Lesson Module: Removing import power point functionality