MDL-47183: viewhiddenactivities should use the module context

Thanks to Paulo Matos for the forum part of this change.
MDL-46712: Center EditPDF window on browser resize / zoom
MDL-41593 admin: use default setting if preventexecpath active

This resolves problems when installing Moodle
and addons when preventexecpath active.

Please note the admin_setting_configfile is still
incorrectly restricted - this will be resolved by
MDL-40949.
MDL-47612 gradereport_grader: Remove max-width for RTL

For some reason, Safari behaves incorrectly when dealing with RTL
content where the table has a max-width of 100%.
MDL-30358 forms: strict validation is too strict
MDL-38065 gradebook: Fix issue with hidden categories breaking rowspan.

Hidden subcategories break the rowspan in the gradebook; this fix corrects
the calculation of the rowspan.
MDL-38172 Lesson: Additional Info not displayed at end of lesson
MDL-29873 Lesson: Essays not shown on grade page with SQL server
MDL-47684 mod: better validation of rating options
MDL-46499 navigation: better enrolled course limit

We now user $CFG->navcourselimit to limit the number of
courses shown in the navigation when browsing another users
full profile. Previously it showed all courses which caused
some slowdown.
MDL-47608 cachestore_mongo: fixed unit test error

If you configured your site to run mongo unit tests and had
the mongo extension and backend installed but did not have the
mongo service running you would get a fatal error when running
the unit tests.
That problem has been fixed by checking the mongo test instance
is ready before returning it.
MDL-46518 navigation: site glossaries now expand properly
MDL-47754 install: fix redirect loop

Conflicts:
	user/editadvanced.php
MDL-47760 grades: dim category name if hidden
Merge branch 'MDL-38065-fix-26' of git://github.com/jmarthaler/moodle into MOODLE_26_STABLE
Merge branch 'wip_MDL-47754_m26_installredir' of git://github.com/skodak/moodle into MOODLE_26_STABLE
MDL-47340 action_menu: selector, RTL, consistency fixes
MDL-47666 DB auth & enrol: unit tests fail with custom DB drivers

Changed to used $DB->get_db_family, rather than hard-coding the list of
class names.
MDL-47673 quiz generator: default grade 100 & fix review options

The review option defaults need to be like what you get from the editing
form, no what is stored in the database, or they don't work!
MDL-47711 behat: make it easier to copy the init.php command.