Added Color class to make dealing with colors a bit more sane (and to allow them to be compared).
Also added some interface buttons to select a color.  They don't do anything yet though.
Cells now take the color of their parents at the time of birth (if the parents are differing colors, then the maximally represented color is used, random choice between ties).  Clicking, dragging, inverting, or using the random fill option will all create cells of the currently selected color.