ORM convenience methods

[scriptbae]

The ORM is currently extremely raw, comprising just models and a call to bootstrap the database.

The models module, or some new, related module should be augmented with convenience accessor-like methods which handle database session management implicit to front-end code.

This includes methods for the following actions:

• CRUD for User
• CRUD for Marker
• CRUD for AdminUser
• CRD for all the *Key models because new key creation should occur rather than an update to an existing key
• CRUD for Challenge
• CRUD for Submission, where status may change
• CRUD for Reservation, where status may change

[cannotparse]

Should be a related module, similar to how this is built.