Fix to our JSON serializer to prevent error ('first' attribute missing).
Merge branch 'master' of github.com:learningequality/ka-lite into release-0.12.0
Fix full_clean (duplicate def on base, and missing kwargs on Device).
Allow Device signed by central server, so they can be modified centrally.
Update version.py
Merge pull request #2209 from learningequality/release-0.12.0

Release 0.12.0