Created hasWriteAccess on Cocomodel, used it for level access
Disabled buttons for non-owners in Article Editor
Fixed a link to point correctly
Added owner-based save enabling on Thang Types. NOTE server-sided doesn't work yet
Enabled Fork button again. Previous commits solve issue #455
Added an anonymous check on the Fork button
Merge branch 'master' of https://github.com/rubenvereecken/codecombat into rubenvereecken-master