memory

* persistent variable usage is now a config option. We can't use them in
the experiments, because the MatLab workers are separate processes and
can't access shared memory, so they all amassed copies of all of the
shows/FFTS. This grew to about 60GB and by that time the speed of
loading show + performing the FFTS was the same as the time it took copy
from the swap file onto the RAM. Because of the way ga wants its
information there is no obvious optimization to keep FFTs in memory.