Don't exceed image ranges

* timestream/manipulate/correct_detect.py (matchTemplateLocation): Be sure that
calculated ranged don't go over the image size nor move to values less than
zero.
Don't depend on accuracy of pot detection

We use the minimum distance between pot centers to calculate the growM factor.
This results in bizarre errors in pot size.
* timestream/manipulate/pipecomponents.py (__call__): Use the median of the
sorted distances to the nearest neighbor to calculate growM.