Monkey patch Engine to copy migrations to host app

This monkey patches the rails Engine to copy the engine's
(answers-core) migration files to the host app as per:
http://pivotallabs.com/leave-your-migrations-in-your-rails-engines/
Include AATO after answers to set migration order

This causes AATO to be loaded (and its migrations) after answers-core.
It also moves all dependecies after answer-core and any other answers-*
plugins.
Remove debugging statements and unused generators
Merge pull request #250 from 18F/fix/249_copy-db-migrations-to-host-app

Copy DB migrations to host app and correctly set order.