Avoid painting -1 values in statistics
Stats optimizations without threshold
Merge branch 'optimize_stats'
Fix teacheradmin urls, add an index one
Add link and copy/paste buttons to nugget's tinyMCEs
Add link and copy/paste buttons to django tinyMCEs too
Use always a '/' at the end of the urls
Some categories can only be assigned by admin
Bugfix, don't lose the admin assigned categories
Show courses' dates in category list
Merge branch 'master' into feature-no-video-quantums