CoreAstroAlgs: added totalExposure as an argument to cas_alg_stats.
CoreAstroAlgs: removed libcfitsio.dylib dependency from CASRegionGrowerSegmenter project.
CoreAstroAlgs: added const qualifiers to all arguments that might benefit from it, in CASAlgorithm+Exposure. Added a function to compute the exposure centroid.
CoreAstroAlgs: refactored some ugly validation code.
CoreAstroAlgs: more refactoring.
CoreAstroAlgs: more refactoring.