Rework gui.

Looks much better and is less quirky.
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.
Create gui in EDT.
Eye-candy: Maximize at start and one-touch expandable field.

- Make window maximized by default.
- Allow to one-touch-expand the JFieldPane to nearly the full window.
  Otherwise, the first this the user always does after startup
  is to hit the maximize-button.
Close scanner instance after usage and free resources.
Implement basic commandline functionality.

- Use the already existing /LICENSE.txt for --license
- Store the --help text in /USAGE.txt
- Prepare for additional commandline arguments
Remove the SKIP2 command.

Change the SKIP icon in the progress.
Consolidate main classes.

- "Genetic" did nothing but preparation work
- "Field" was the real main class
- Move gui related resource loading to class "Gui"
Set parameters from command line.

Have a switch to turn on and off immutable parameters write protection.
This work is based on a patch by Ben Wiederhake.
Introduce simulation state.
Gui for simulation state.
Exit program gracefully when closing the window.
Add more javadoc.

Update Readme as well.
Clear field on simulation stop.
Collect statistics.

This work is based on a patch by Ben Wiederhake.