ADD: CSAPR CMAC testing

My notebook for CSAPR CMAC testing. The latest commit includes my
testing of the extra volume preparation to the 4DD algorithm. The extra
volume preparation includes using the normalized coherent power and
cross correlation ratio fields to further remove noise and second trip
echoes before velocity correction.

Basically what I have found with the 4DD algorithm is that noise in the
velocity field can introduce artifacts, especially around cloud edges,
and that the extra volume preparation helps remove most of these
artifacts.