genetics: Change the default settings

As many people have pointed out, the default settings converge quickly
on a reasonable likeness, but then quickly plateau and fail to improve
beyond that point. This patch changes the default settings to try and
address this, by using large populations with decreased mutation,
represented using simpler triangles.

    Population size     40    -> 50
    Selection cutoff    25%   -> 15%
    Mutation chance     2.4%  -> 1%
    Internal resolution 70x70 -> 75x75
    Number of polygons  120   -> 125
    Number of vertices  6     -> 3

Results from 1 minute of simulation before this patch:

    Number of generations       438
    Average time per generation 13.61 ms
    Highest fitness             98.98%
    Lowest fitness              94.01%

And after:

    Number of generations       580
    Average time per generation 10.31 ms
    Highest fitness             99.33%
    Lowest fitness              93.92%