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-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-40621 fixed small bug in function editor_tinymce_plugin::fix_row()
MDL-39563 Fixing mobilecssurl is not being returned in WebService, phpunit tests
MDL-38747 blocks: course format options 'numsections' is required to display the block
MDL-40574 remove forgotten $delete from editor subplugins page
MDL-40569 fix empty CSS files after cache purging
MDL-40558 skip admins and guest when deleting incomplete users
MDL-40549 remove unused legacy assignment upgrade tool
MDL-40633 filter_urltolink breaking some image links.

This was a regression caused by MDL-22390. HTML like
<img src="http://www.example.com/logo.gif" />
was being broken.
MDL-40475 add alternative component cache location and other improvements

Improvements include:
* Alternative location might be useful when server administrator wants to maintain
  a local copy of component cache instead of using shared $CFG->cachedir.
* Component caching is now enabled in behat tests which should improve performance.
* Standardised ignoring of component caching.
* Fixed debug mode in ABORT_AFTER_CONFIG scripts.
* General documentation improvements.