Extract models into a Core/Common package

[justinsacbibit]

Both trucksu-web and trucksu-bancho use the same database, and thus they use the same models. The models are currently within trucksu-web.

trucksu-bancho gets access to the models through the use of a gitsubmodule that points to trucksu-web, which makes the entire trucksu-web application a dependency for trucksu-bancho.

It might be a better idea to move the models into a separate package, which trucksu-web and trucksu-bancho would both use.