autorectify.py: Make RectifyParams.size[] float instead of int
autorectify.py: Improved debug prints
autorectify.py measure_rectification_one(): Drop useless math.log() call
autorectify.py MAX_RADIUS: Globally accessible constant for RectifyParams.maxsize
autorectify.py RectifyParams.xytilted(): Split out xytilted_tau()
autorectify.py: Importance sampling based on tile brightness when evaluating lens rectification