OO-1882: in assessment mode editor, highlight the right field if course elements options are selected but not the course elements

OO-1879 implement context help using confluence for course help SPI. Course help only used for main manual link.

OO-1876: don't break the recursion for the project broker course element, don't take it as assessable, but takes its children elements

OO-1859: fix controller disposed if someone in member management of course selects a group and close the group with the red cross

OO-1864: upload attachments for new threads, dedicated mark as read messages for newly created message

OO-1856: fix select all + click on pageing, next and previous beahvior on old table implementation to mimic 10.3

OO-1855: add a configurable possibility to prepend the external id of course to their WebDAV folders