Move persistence logic to CASino

The current workflow of using a Rake task to load the CASino schema into the DB and then migrating seems a bit fragile. My biggest concern is that when my teammates clone my application, they will have to be aware of an additional, non-standard, bootstrapping step in order to get the application up and running. This is due to the fact that the required CASino migrations won't be committed to my application's repo.

This PR moves all of the persistence logic to [CASino], making CASinoCore more ORM-agnostic. It also moves anything database or ActiveRecord related functionality into [CASino] as well

See also:
* [Devise](https://github.com/plataformatec/devise/tree/master/lib/generators/active_record)
* [Rails](https://github.com/rails/rails/tree/master/activerecord/lib/rails/generators)

[CASino]: https://github.com/rbCAS/CASino