Refaktor

Added a test app ('baseuser') in bb_accounts that is added to INSTALLED_APPS when the suite is run. The baseuser app provides a custom TestCase object that dynamically loads the baseuser app, and its models, into the test database. For now, the 'baseuser' app defines a TestBaseUser that implements the abstract BlueBottleBaseUser.

The bb_accounts test suite includes a simple demo testcase that uses the implemented abstract base user.

You can run the unit test like so: python manage.py test bb_accounts.BaseUserTests --settings=bluebottle.settings.testing

This PR also includes two small fixes, one typo fix and one dynamic loading of the Task model in the HomePage app.