MDL-43684 Course: Correct showing and hiding of resources on drag/drop

This was caused by an issue with String casting in JavaScript.
In JavaScript, "0" evaluates as a truthy value.
MDL-43804 themes: Update css not to use r0 and r1 identifiers for table rows
MDL-43838 behat: Clean theme compatibility with small and medium screen sizes
MDL-42882 upgrade: unit tests for root folders upgrade

Just verifying the original behaviour
MDL-42882 upgrade: improved SQL query

Kudos to Tim Hunt who came up with this, on mysql with 4 milion
records (and a fast SSD) the performance difference is:

Original: 36.83 sec
New query: 8.63 sec
MDL-43200 WebServices: Reset Instance variable
MDL-32724: LDAP Auth function user_update() returns true even if update has failed
MDL-43978 badges: Display error message to guest users viewing "My Badges" page
MDL-43774 badges: Stop overriding default course navigation
MDL-42882 upgrade: Improvements to upgrade code

Suggested by Petr:
* Don't rely on single user for upgrade
* Make the pathnamehash generation a bit clearer (and add
  a test to verify its correctly formed).
MDL-43946 gradebook upgrade Improve SQL to find duplicate sortorders.
MDL-44029 mod_quiz: Fixing group deleted handler so it does not remove user overrides.
MDL-43978 badges: Fix lang string
MDL-43267 Javascript: Improve accessibility of keyboard move

Change the keyboard move descriptions to allow for more detailed
descriptions such as:
* "After 'X'"; or
* "To top of section 'Y'"
MDL-43267 Javascript: Remove aria drag/drop related attributes for drag/drop

Since we provide an alternative interface rather than describing the
locations for each drop, we should not add aria-grabbed, or
aria-dropeffect.
MDL-43267 Javascript: Improve focus before and after drag/drop
MDL-43969 Forms: Adjust ARIA attributes for short forms

The aria-live="polite" attribute is incorrectly added to the fieldset,
causing the entire fieldset to be read out on change in some browsers. This
is unnecessary.
It also does not announce the current state of the fieldset (collaped or
open) and should.
MDL-43992 Javascript: Remove <return> key listener for confirmation

The listener was previously confirming, even when the cancel or 'No'
buttons were selected. However, having the default action as 'Confirm'
seems dangerous in this situation, so removing this option entirely.
MDL-43994 Blocks: Hide the move icon when blocks are docked
MDL-44020 Add core_calendar_get_calendar_events function to the moodle mobile core service