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.
 
The problem is that I was thinking about samples and not pixels. Samples are taken at discrete points and as how I see it a pixel is a average over a certain interval, the pixel length.