Brownju/bug/47

Added a module for validating user input, moved the location of orvsd_central.database.Model to orvsd_central.models.Model, and added tests to general.register() which the function itself still needs to be tested for correctness.
I don't think this is needed here. Since the transaction doesn't *actually* go through and it just raises an error, there's nothing to rollback. rollback() is useful when you're making multiple db transactions in which if any fail you want nothing to happen.