Downgrade max Django supported version to 1.8
Downgrade max Django supported version to 1.8

The WebUI still has some minor issues with Django 1.9


Former-commit-id: c808033b5c84f31c4d2b1f11a0a349b87f11a655
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine