* Refactor. Extract Robot#move.
* Enable top-level test and make it pass.

I'm at the stage where all of the commands used in that test work.
* Amend top-level test to include all possible commands.
+ Move outside of the table is ignored.
* Remove obsolete code.
* Refactor.

Place inner class definition first, constants after that.
* Refactor.

The class holding robot coords on the table and direction is better called
State, not PlaceCoords.