Merge pull request #794 from diox/fix-guess_features_existing_apps

Overwrite empty app features profiles in update_features
Use DATABASE_URL instead of DATABASE_* settings.
remove unnecessary imports
create models draft (bug 879519)
comment out theme-checksum migration
Revert "comment out theme-checksum migration"

This reverts commit 2145b97d440cecb1646793ee7d91813698c4388c.
fix theme description migration
update template
lower log level on some very common calls
fix margins on "Manage Versions & Status" page (bug 880011)
we have too many tabs on desktop (bug 877472)
Script for fixing badly decoded theme descriptions. (bug 784874)
unskip test, remove temporary code
bump
Drop filter by app_type for android (bug 878918)
Added special time limits for marketplace reindexing (bug 880523)
Updated reindex_mkt to override celery soft time limits (bug 880523)

This update also uses celery 3's chains instead of using a tasktree.
Auto-create AppFeatures when app version created (bug 880328)
Forgot to `run` the migration
delete test for deleted code