Resolution-Visualization script shows lines correctly

The AnalyzeGrid script read (for the moment) one image, makes the user
select a ROI and plots the brightness values in this ROI.

This makes it possible to visualize the resolution phantom, i.e. detect
if we can distinguish xx lp/mm.
Optimize figure display and save output
Use os.system instead of subprocess

I didn't manage to make subprocess.Popen work (probably missed some
escaping), thus simply calling os.system to transfer the TAR files...