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.
 
It is necessary to overspan te range of 0 to and with lx with Nx samples. So not doing it would make the range from dx to and with lx or 0 to lx.