make_fft_filter function in aoAlg.py assumes a square image

[NickHallPhysics]

make_fft_filter function in aoAlg.py assumes a square image when constructing the tukey filter (line 141). Non-square images result in a error at line 143:

ValueError: operands could not be broadcast together with shapes [shape1] [shape2]

[carandraug]

For reference, original issue was microscope-cockpit/cockpit#679