Added script to read images from camera(s)

At the moment the python script ReadCamera.py only reads out images from
the "the imaging source" camera, but eventually it should evolve into a
full fledged camera reader, once the development boards from Aptina are
here.
The committed version is the initial version, written in an afternoon.
Since the script outputs snapshots, I also updated the .gitignore
Updated setup instructions of the TIS camera

Mostly added some details about the window size, since that was quite
bothering...
Updated Dose calculation and Spectra-plotter.

Since we saved the spectra a tiny bit different, we also had to change
the way we read them in.
Additionally, I updated the dose calculation script, to be a bit more
meaningful.