MDL-43325 JavaScript: Set a default visibility for most Moodle dialogues

We used to ignore the 'visible' field in the initializer, but now we hide
dialogues if visible is false. This was an unintentional change from the
stable API and means that confirmation boxes, alerts, and exceptions are no
longer shown by default.
MDL-34182: Add functions to warn of output in AJAX scripts

We need to be able to capture output when including contributed code as it
may add additional content which makes makes the json we output invalid.

We only warn of these errors if the site is in debugdeveloper, otherwise
we silently drop them.
MDL-34182 AJAX: Change to use shared method when checking the siteadminbranch for invalid output
MDL-34182 Repositories: Check for and warn on invalid output in the file picker
MDL-35032 mod_book: 1.9 backup restore convertis files to book area
MDL-43250 Assign: separate groups mode fix

When in separate groups mode, only get graders in a group that is in the course module grouping.
MDL-30195 portfolio_googledocs: Allow export of rich HTML
MDL-43410 JavaScript: Stop event propagation when opening the action menu

In certain situations, the click event is propagated through to the
hideIfOutside and immediately closes the menu.

This happens when blocks are dock for example.
MDL-43438 mod_assignment: Prevent double inclusion of plugin files
MDL-41246 cache: Fix PHP notice of non well formed numeric values for the memcache store
Automatically generated installer lang files
MDL-41788 theme_bootstrapbase: Custom menus - sub-menus breaking.
MDL-43318 Assign: Fix bug when editing previous attempt feedback
Merge branch 'install_26_STABLE' of git://git.moodle.org/moodle-install into MOODLE_26_STABLE
weekly release 2.6+
MDL-43367 stop returning of bogus context children when path unknown

This also prevents deletion of system context.
MDL-43314 make float serialize consistent on all systems

This should resolve problems with plugin version change detection.
Merge branch 'MDL-34182-26' of git://github.com/andrewnicols/moodle into MOODLE_26_STABLE
Merge branch 'MDL-43325-26' of git://github.com/andrewnicols/moodle into MOODLE_26_STABLE

Conflicts:
	lib/yui/build/moodle-core-notification-dialogue/moodle-core-notification-dialogue-min.js
MDL-34182 js: fixed typo in ajaxException use