OO-848: extended postCopy() method with source and target Course to get the copy of a whole course working

OO-1501: fix rs if the file has no extension in the list of wiki files, fix span not closed, fix math insert script

OO-1440: use callout for filters and sorts of flexi tables and tables, missing i18n key for checklist in archive, fix 2x escaping in the group list of assessment tool, fix floating image in test statistics which breaks layout

OO-1499: delete export folder after the import of a course, upgrade task which delete these folders on current courses

OO-1483: concat instead of StringBuilder, optimize label text renderer, don't check number generated id to secure it in javascript varaibles

OO-1493: update to TinyMCE 4.1.9, do the remove of the editors in the DOM replacement routine in function.js ( this prevents leaks of editors in some case )