OO-1546: hardened the remove method against unexpected case, identity not participant, don't remove the last user without check it...

OO-91: add more informations to the list of groups and assessed identities and fix some other issues

OO-991: implements relative dates for assignment, submission and solution due dates, enhance the reminders rules engine to support them

OO-1544: better check of the validity of the last history point used in the "close" method of the course tab

no-jira: use javascript to fill the import textarea as copy/paste is not supported on the different browsers and platforms i want, add a selenium test which import an existing user and change its last name and password

OO-1539: add a timeout to the focus command, jQuery dialog focus something on its own and we must wait it is finished with it