Implemented and exposed GUI for the additional options of histogram thresholding.

Very preliminary test was performed of optimal histogram thresholding using "Bimodal Gaussian representation".  Case ZAMB.  Approximation done by Global optimization in R6 space, with 1M iterations in this experiment.

ZAMB: original histogram for Breast Mask

Original histogram thresholded by OTSU algotithm

BImodal Gaussian approximation and simple minima threshold 

Bimodal approximation threshold on the original histogram

Global optimization framework:  full parallelism of the main loop.  This allow the application programmer not to bother with parallelizing the cost function thus greatly simplifying the usage.