MDL-41114 Avoid unnecessary retrieving of coursecat from DB

- course category depth can be estimated in make_categories_options() by the number of separators
MDL-35919 - Activity Chooser - Adding Aria attributes to improve accessibility
Merge branch 'MDL-30001_25' of git://github.com/jmvedrine/moodle into MOODLE_25_STABLE
Merge branch 'MDL-27655_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE
MDL-39507 questions: fix pluginfile URLs before format_text.
MDL-39507 questions: fix pluginfile URLs before format_text.

This commit build's on Jean-Michel's work, tidying up a few lose ends.
Merge branch 'MDL-35934_m25' of git://github.com/rwijaya/moodle into MOODLE_25_STABLE
Merge branch 'MDL-35919-25' of git://github.com/phalacee/moodle into MOODLE_25_STABLE
Merge branch 'MDL-35931-25' of git://github.com/phalacee/moodle into MOODLE_25_STABLE
NOBUG: fixed whitespace
Merge branch 'MDL-30895-25' of https://github.com/mouneyrac/moodle into MOODLE_25_STABLE
Merge branch 'MDL-40996_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE
Merge branch 'MDL-40852_25' of git://github.com/dmonllao/moodle into MOODLE_25_STABLE
Merge branch 'MDL-41033_m25' of git://github.com/rwijaya/moodle into MOODLE_25_STABLE
MDL-41050 Progress bar: Width parameter does not work
Merge branch 'wip-MDL-41114-m25' of git://github.com/marinaglancy/moodle into MOODLE_25_STABLE
Merge branch 'MDL-41091_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE
Merge branch 'MDL-39691_25' of git://github.com/jmvedrine/moodle into MOODLE_25_STABLE
Merge branch 'MDL-41045-m25' of git://github.com/sammarshallou/moodle into MOODLE_25_STABLE
Merge branch 'MDL-39507_25' of git://github.com/timhunt/moodle into MOODLE_25_STABLE