bug fixes and modifications to contig cost function (this is goooood)

* contig thresholds are now based on the mean of each half of the
interval, this is a massive improvement. I noticed that there was also
some variation here. this totally removes the hacky nature of the
threshold as the sub distributions are normal
* the disincentive is now multiplied by an inverse gaussian window
* the values are now normalized by the width, not the width progression
(i)
* better information displayed on the cost map image (drawsimmat=1)