Ignore .scad files for labeling

If you want to have labels on your drawing, you'll have to look into the
code and grab the relevant files from
http://www.cannymachines.com/entries/9/openscad_dimensioned_drawings
Make CalculateDetector.py work again

And include the bash script to run it with a bunch of parameters.
Also ingnore the image directory with the output of this script
Correct typo
Draw and calculate with diagonal as base length

We now use the sensor and FOV diagonal as "base length" for calculating
everything, so we don't have a different x- and y-magnification.
Use the division we expect by importing it from the `future`.
There's no need to draw and save the image twice.