add postgres Fact model, update views, tests

* awx.main.models Fact added
* view host fact and timeline updated to use new Postgres Fact model instead of Mongo
* Removed license set start Mongo logic
* added View tests
* added Model tests
* Removed mongo fact unit tests
* point at modified jsonbfield that supports sqlite storage driver
* postgresify fact cache receiver
* test OPTIONS endpoint
* Note: single fact view not implemented yet.

requirements/requirements_dev.txt

@@ -7,3 +7,4 @@ pytest
 pytest-cov
 pytest-django
 pytest-pythonpath
+pytest-mock