Many fixes to keep this from crashing due to changes in parameters,
loading/clearing etc.
Add functionality for hiding/showing ROIs associated with Crystal area
used for calibration.
Disable Find Crystals button until we can determine a better way to
specify the regions automatically for now at least, the crystal arrays
overlap and have low intensity (making it hard to find the lines to
Added a menu item which allows showing the data points to be used in
calibration.  There are some significant regions of overlap that should
probably be avoided.  This should help find them.