spot analysis for peak intensity correction

[bbean23]

Note: this ticket got unwieldly big. Splitting between here and #91

Add spot analysis code to analyze peak intensities of a heliostat. The necessary features include:

• area of interest cropping [af]
• over-exposure detection & warnings [ag]
• tagging images as NULL (aka dark aka not exposed to heliostat) or active (aka active aka exposed to heliostat) [ah]
• averaging multiple images [u]
• image subtraction, to get relative flux to a NULL image [a]
• filters (gaussian and box) [ai]
• centroid/peak value computation [e, aj]
• logorithmic intensity scaling [ak]
• false color visualization [al]
• over-exposed pixels visualization [am]

Additional features that might be helpful include:

• directory watcher image source, to introduce new images to the pipeline as they are added to the source directory
• image translation correction based on tower fiducials
• pixel intensity to actual flux correction [s]
• image scale tagging (how many meters is a pixel?)

[bbean23]

closed via #87, see #96 for the next stage of this effort