MDL-45192 assign: added behat script & new definitions to handle alert dialog

The behat script is to test the batch action to lock and unlock submissions.
The new definitions are to prevent the "unexpected alert open" error in Selenium.
MDL-45192 behat: Replacing specific-selector steps by a generic one

Having a I click on we can use all our selectors rather
than having multiple steps for the same purpose. This
step allow us to manage JS native dialogues without
having to fail a scenario.

Credit for Mohamed Alsharaf.
MDL-45607 events: changed the context passed to the user_profile_viewed event
MDL-45623: Fix assigned users count on role delete confirmation page
MDL-45629 mod_assign: removed use of '$this->objectid' in the submission_status_viewed event
MDL-45650 events: ensure correct objectid passed when triggering user_profile_viewed event
MDL-42526 mod_assignment : fix record insert with assigment.id 0
MDL-44014 Navigation: Set the correct context when retrieved via AJAX
MDL-45660 question statistics: make comparison more robust.
MDL-45635 javascript: Make core dialogue translatable
MDL-45686 qtype_multichoice get_num_selected_choices return wrong result
MDL-45499 admin: fixed error when displaying page settings
Merge branch 'MDL-42526-master' of git://github.com/jamiepratt/moodle
Merge branch 'MDL-45607_master' of https://github.com/markn86/moodle
Merge branch 'master_MDL-45623' of git://github.com/totara/moodle
Merge branch 'MDL-45635-master' of git://github.com/andrewnicols/moodle
Merge branch 'MDL-45686' of git://github.com/jmvedrine/moodle
Merge branch 'MDL-45660' of git://github.com/timhunt/moodle
Merge branch 'MDL-45192_master' of git://github.com/dmonllao/moodle
Merge branch 'MDL-45650_master' of https://github.com/markn86/moodle