Clarify workflow for Segmentation B

[danielmwatkins]

The function segmentation_B is an image binarization algorithm at its core. Most of what happens in the function is the following

1. Threshold-based brightening
2. Histogram adjustment with GammaCorrection algorithm
3. Application of cloud mask
4. Threshold-based binarization
5. Application of imfill to binarized image

At the end, the segmentation_A result is intersected with the binarized, in-filled image.

Two of the along-the-way matrices are also returned to be used in segmentation_F. We might be able to make the along-the-way images (segB.not_ice, segB.not_ice_bit) optional outputs to simplify the purpose of the function.