MDL-38979 Add lang menu to empty custommenu

Show custom menu even when no custom menu items if lang menu needs
to be shown.
MDL-39388 bootstrapbase: Add bootstrap tab renderer

This adds a renderer that outputs standard bootstrap HTML for tabs,
deletes styles that were previously required to make Moodle tab HTML
superficially resemble Bootstrap, and tweak the responsive code that
makes tabs stack on phones to account for the change too.
MDL-39290 Collapsible editor tab needs some mouse-over CSS
MDL-31193 display the correct and translated token valid until date
MDL-29472_m WebServices Cohorts
MDL-39520 always include lib file when accessing coursecat class
MDL-37552 external_format_text: missing require_once filelib.php (shared credits to Adam Fredericks for report and patch proposal)
MDL-39545 mod_assign: prevent notice from displaying when course module id does not exist
MDL-39552 Make behat code re-entrant safe

With yui combo in action, some times setup.php is
included more than once. So it's mandatory to
guarantee that code until ABORT_AFTER_CONFIG_CANCEL
can be executed safely multiple times in the same
request.

This change just prevents the behat section to be executed
more than once. All the values that are set within it
should be already defined for the re-entrant call.
MDL-39462 added missing clearing of coursecat cache
MDL-39397 badges: Handle course badges when course is deleted
Merge branch 'MDL-37552-master' of git://github.com/mouneyrac/moodle
Merge branch 'MDL-29472_m' of git://github.com/andreabix/moodle
MDL-29472: Cohorts webservice - fix numerous access problems and add to the unit tests.

Also allow 'system' as a category type to allow you to create/update system wide cohorts.
Merge branch 'MDL-39388-master' of git://github.com/ds125v/moodle

Conflicts:
	theme/bootstrapbase/style/moodle.css
MDL-39388 corrected tabs renderer to deal with old code
MDL-38594 change course listing heading font size back to default
Merge branch 'MDL-31193-master' of git://github.com/mouneyrac/moodle
MDL-38532 behat: Hardcode latest 2.5 moodlehq/behat-extension version
Merge branch 'MDL-39542-master-int' of git://github.com/FMCorz/moodle