Introduce Field.reset(), reorder Genetic.main().
Add Parameter.GRID_GAP and Parameter.GRID_VISIBILITY.

Default display mode stays pixel-identical to (all) previous versions.
Added shading of entity color to indicate entity health.
Implemented and document keybindings to close window.

Implemented both Ctrl-Q and Ctrl-W since the user doesn't want
to spend time memorizing or testing which one it was.
Let entity eat food that drops on their position, if entity is waiting.

This isn't exactly what we want Programs "encourage" to do,
but it feels "more natural" this way.