Split the state machine into state, state_machine, history, and command.

* Pull out core state machine code from the original state_machine.js.
* Update code and tests for use in new state machine.
* Add new state_machine core.
* Add history.
* Add command.
* Update tests.
* Rename resources/state_machine to resources/state

This should simplify a lot of these "cancel email verification" problems.