Corrected embarassing typo and updated README
Draw more precisely

Removing unnecessary code at the end.
Draw the start/end of the beams at the correct CMOS positions.
Add proper coloring of the (3) beams.
Change the labeling in the `add_lens` function.
Draw the whole box and backplate
INI file is now more informative and `pep8`y

The command-line output tells you the size of the images, so there's
less to think about