Update audit system to allow deleting
Update audit system to allow deleting

Previous initialization order allowed us to fake deleting by calling
`super(UserTrackable, self).delete(...)`. This worked because
`models.Model` was last in the declared super class chain.

Now we assume there is a undeclared dependency in that subclasses of
`UserTrackable` must also be subclasses of `models.Model`.

The obvious solution is to make `UserTrackable` itself a subclass of
`models.Model` however you end up a non-tree like inheritance hierarchy.

clever-crow-consulting/otm-core,maurizi/otm-core,maurizi/otm-core,recklessromeo/otm-core,RickMohr/otm-core,clever-crow-consulting/otm-core,maurizi/otm-core,RickMohr/otm-core,recklessromeo/otm-core,recklessromeo/otm-core,RickMohr/otm-core,recklessromeo/otm-core,maurizi/otm-core,clever-crow-consulting/otm-core,RickMohr/otm-core,clever-crow-consulting/otm-core