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.
Clear field on simulation stop.