Run for 15k generations against SuperSpinBot

Same setup as before, but run until performance had clearly levelled off. Turns
out to be at about same level as before; the slightly about 50% score is
slightly misleading as this is the best of each generation therefore benefits
from the most favourable random fluctuation - they only tend to score a little
abouve the average of 25%ish.

I suspect that genetic diversity has been destroyed as the behaviour seems to
change very little once it has established the 'drive back and forth spinning
the gun and shooting when it sees an enemy' tactic.
Added log missing from previous commit
Rewritten mutations

Added breeding mutations, whereby the parent strings can be 'incorrectly' chosen
and assembled in the wrong order, and large scale mutations, whereby large
chunks can be deleted, repeated, reversed or moved.
Run for ~2k generations against SpinBot

Achieved a much quicker rise in performance than previous runs, also managed to
achieve a higher performance - running average of 97% with some 100% generations
Added extra digit to winner directories for over 10k generations