MDL-40468 libraries: removed usages of get_related_contexts_string() in core

Also tidied up the functions by removing unused parameters.
MDL-40642 set more restrictive umask and use proper permission for new dirs and files
MDL-40642 use this->cfg in local file store when fixing permissions
MDL-38867 remove Google spell checking option
MDL-39635 behat: Fixing line breaks

Not supported by Windows OSs.
MDL-39635 behat: Replacing hardcoded language strings

Using get_string() instead.
MDL-39635 behat: XPath cleanups

- Escaping steps arguments redirected to other steps
- Adding normalized-space() in all contains() assertions
- General xpaths review
- Convering provided xpath text strings to xpath literals
  to avoid problems with arguments containing both single
  quotes and double quotes
MDL-40123 behat: Show all of form's elements changes.

* Avoid waiting until Show more... links appears if we
  already waited.
* Use collapse/expand button rather than clicking on
  each of the form's fieldsets.
MDL-40649 libraries: deprecated get_recent_enrolments()
MDL-20609 quiz tables: improve layout for long cell contents.

By allowing more wrapping.
MDL-40480 tablelib: specify charset in XHMTL downloads.

Thanks to Jürgen Zimmer for the suggestion.
MDL-40719 pluginfile.php: the file API is now stable, so hide debug.
MDL-40787 Forum: Remove old commented-out code from forum
MDL-40785 question instances report: ignore subquestions

We should not count subquestions of cloze questions (parent != 0) but we
do want to count random questions (parent = id).
MDL-40788 Profile: Remove debugging code displayed on profile page
Automatically generated installer lang files
MDL-23493 add support for theme fonts
MDL-23493 allow numbers in components used in CSS placeholders
MDL-40545 add $CFG->localcachedir intended for local caching on cluster nodes
MDL-40545 convert js and theme resources to localcachedir