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.
 
Its true that X,Y are not needed, still I think x and y should be supplied. Just for the reason that Ii need to be delivered with the correct spatial dimensions, off course we can make a generic function.