no-jira: backport fix for the escaping of already escaped characters by TinyMCE in enrollment course element

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

OO-1004: encode softly the webdav names for group and resources to preserve as much as characters as possible

OO-1004: encode softly the webdav names for group and resources to preserve as much as characters as possible

no-jira: enhance course db to list of used categories, and accept repository entry keys as course id

OO-936: implements course element "check list", enhance the flexi-table with sort, filter and export, enhance publish process with an update step, upgrade pdfbox to version 1.84