MDL-44891 Behat: Add step to check attribute

This commit creates a Behat step of the form:

Then the "title" attribute of "Toggle visibility" "button"
should contain "Show"

This is useful because unless I missed something there is currently
no step that checks attribute values; this seems like a simple
generic step. Behat is intended to check user-visible effects in
the resulting HTML, and sometimes these effects are implemented
using attribute values (two common examples are the alt= attribute,
which is visible to screenreader users, and the title= attribute,
which is visible to all users; there's also the src attribute of
images, and lots of other possibilities too).
MDL-44940 quiz editing page problems from MDL-43749.

* If the quiz starts with an empty page, you could not move the first
question up onto it.
* Adding page breaks in the middle sometimes added them in the wrong
place.
* Adding a new page at the end is problematic, and here we fix it as
much as possible, by letting you move the last question down to create a
new page. This needs MDL-40987 to be fixed properly.
MDL-44948 add tool_qeupgradehelper to the list of deleted plugins.
MDL-36141 course Define role to limit access to Other users.
MDL-39833 course: require token change

MDL-39833 course: require token change
MDL-44967 upgrade: fixed theme removal when themes have been removed already
MDL-41511 blocks: improved how custom block regions were being rendered.

There is a new theme property 'blockrendermethod' that can be set by the
theme in its config.php and tells Moodle what method it is using to render
blocks in the layout files.
Either blocks, or blocks_for_region.
Then when adding custom block regions to a page content we ensure we use
the same method the theme is using elsewhere.

This is really a hack becuase we (I) didn't properly deprecate
blocks_for_region when I added the blocks method.
MDL-41551 blocks: added tracking and recognition of custom block regions
MDL-41551 theme_base: improved custom block region handling for base
MDL-42317 theme_bootstrapbase: more responsive styling for forms with blocks pre && post
MDL-42317 output: reviewed standard/base layouts and converted where a better option was available
MDL-44882 always set maintenance mode on non-cached admin pages

This should resolve all issues with themes during upgrades.
MDL-44944 theme_bootstrapbase: fixed content spacing issue with docked region

Thanks Mary Evans for the peer-review and better solution
Merge branch 'MDL-44949-master' of git://github.com/damyon/moodle
Merge branch 'MDL-44846-master' of git://github.com/damyon/moodle
MDL-44971 Add hook to "add_attempt" for mod/assign/submission plugins
MDL-44765 Atto: Fix the accessibility warning events for image dialogue
Merge branch 'MDL-44940' of git://github.com/timhunt/moodle
Merge branch '41551-27' of git://github.com/samhemelryk/moodle
MDL-44758 editor-atto: prevent table-in-table creation

Prevent new table creation, displaying table context menu instead when cursor is within caption, when multiple cells are selected, when selection contains both nodes within and outside of the table, and when selection contains nodes from multiple tables.