Change renderer to JavaFX

[chillibasket]

After trialling the other renderer options available in Processing, I noticed that JavaFX (FX2D) has significantly better performance than the standard renderer. On average, CPU usage was down by 90% and frame rate remained consistent at 60FPS. However, JavaFX has some compatibility quirks which need to be resolved first:

1. On exit, the window is closed but the process does not exit (it continues as a background process). Implement a proper exit() function to ensure correct closing behaviour.
2. There is a different method of setting the minimum window dimensions.
3. The normal File dialogues and SWING popup windows do not interact properly with JavaFX and should be replaced with the native FX variant of the dialogues.

[chillibasket]

Implemented in commit 458847c. All the identified compatibility quirks have also been resolved.