color overlay is not intuitive nor efficient

[7yl4r]

It is perhaps not obvious that a color overlay with the 'constant' rule is being used, and this leads to some strange usage requirements in some cases. For instance: cell layers need to be deleted or rules need to be reset after running lifeGenes scripts.

A possible improvement: adapt the 'constant' rule to use GoL rules (or possibly highlife). This rule would treat all non-zero states as state 'one' in GoL rules. This way the rule could maintain the color display with many states, but also not need the functional cell layer below.

This could lead to performance gains as well. Because the 'update' method which reads the functional layer and updates the display is one of the top cpu-hogs, improvement here could be sizable.