MDL-39563 Fixing mobilecssurl is not being returned in WebService get_siteinfo function
MDL-35131 Caching: Purge all will clear course modinfo cache - Thanks to Thomas for patch
MDL-40412 course Expanding the height of module description fields.

Expanding the default height of mod descriptions to 10, which gives
you 3 real lines once TinyMCE Loads.
MDL-40440 Backup: Skip files that already exist
MDL-40112 badges: Drop unused image field from badge table
MDL-39926 SCORM: new Objectives report type
MDL-39812: bootstrapbase theme: Fix breadcrumbs layout for narrow screens
MDL-39812 clean theme: fixed breadcrumbs layout for narrow screens
MDL-40524: mod_wiki: Display comments in order
MDL-40555 cache: Static store is searchable
MDL-40195: mod_assign: Display grades when quickgrading to 2 decimal places
MDL-40538 caching: Use isset for performance

isset is much faster than array_key_exists. For caches we need to
ensure as much performance as possible. To all null to continue to
be stored and provide correct results, non ttl also now saves in
$this->store[$key][0].  As isset($this->store[$key]) will return
true in all cases.

time() as found in cache::now() can be slow on some platforms and
we shouldn't bother checking it unless needed. It also stops non-ttl
caches paying the ttl price.

Unit tests were adjusted to ensure null is still handled correctly
when we are only using isset.
MDL-40426 - Libraries: Deprecate mark_context_dirty().
MDL-40428 Libraries: Deprecated delete_context
MDL-40621 fixed small bug in function editor_tinymce_plugin::fix_row()
MDL-40431 libraries: deprecated get_context_url()
MDL-40431 libraries: added another PHPUnit test to ensure deprecated function returns the same as the replacement
MDL-40462 libraries: deprecated get_course_context()
MDL-40462 libraries: added another PHPUnit test to ensure deprecated function returns the same as the replacement
MDL-40464 libraries: Deprecate get_user_courses_bycap()