no-jira: add a JUnit rule to take screenshot of the browser which make an error during a selenium test, hardened the popup to create feeds

no-jira: small selenium test to create and delete a business group, selenium to test concurrent editing of a course

OO-1443: upgrade selenium to version 2.46 which is much quicker as 2.45 and fix an issue with Firefox 38, fix a race condition in the business gorup tree which make the links unusable, fix a upper/lower case issue if the selenium tests are run with PostgreSQL

OO-991: selenium test for the group task with standard settings and all steps made with three hands, selenium test for enrollment with unlimited sized groups ( follow a bug with this particular setting )