create an .mdo for continuum's model

Something continuum needs, but will be needed in general, is a standard
way to incorporate a modello model into application.

Please make the modello model for Continuum.

Initially, just create the .mdo for the hand coded data model classes for review. After that, the hand coded classes can be replaced with the generated model, but this may be dependant on the m2 lifecycle being able to do that.

Use the prevayler store for prototyping.