Bad Pixel Mask - flag hot pixels and exclude from search

[bhilbert4]

Pixels that are hot enough that they are saturated all the way up the ramp will have a slope of zero in the ramp-fit output images. These will then be mistaken for dead pixels in the dead pixel search.

Add code to examine dark ramps, identify (and flag?) these hot pixels, and then exclude them from the dead (and noisy/open?) pixel searches.