no-jira: fix unit test of the  courses REST API with PostgreSQL, order of the courses is not defined

OO-1042: check the boundaries of the hibernate bag before add a checkpoint, clean the velocity container and reload all data after a save...

OO-1038: better check of long without exception, try and catch in PersistingCourseGroupManager, unit tests

-no-jira: replace escaping with antisamy for group description as the description is edited with TinyMCE (which already escape special characters)

OO-716: replace the flot library in the course statistics with the bar chart component which use d3.js