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.
 
Are other groups already using X and Y? Will they use it? Can they generate it from x and y? Or even better, can there be a generic function that generates x and y that other groups can use? Then you don't need to return X and Y. By not generating them the code is easier to read and to understand. (You actually don't need (X and Y) but only (x and y)).