WFS update, and added function for rectangular setups in the main

Increased the readability of mainWFS.py.
Normalized the intensity distribution and the lensletCentx/y.
Added support length for FFT in the parameters for the sensors.
Added function in main to handle rectangular lenslet configurations.
 
After spending some time reading and analysing the code, I have a suggestion here. Can you return only xPhase and yPhase, and generate the meshgrid inside tiltPhasePlane? That would make it less confusing to read the code and reduce the number of returned values (which also makes it easier to read).