Center films around 0
If I film is not centered around 0 in z-direction it runs into a lot of numerical trouble. Therefore, I suggest that fleur just shits the film by itself so, that it is centered.
Alternatively we could give a waring to users telling them, that it's not centered.
Why is this feature needed?
This would be much more user friendly. Now users get something along the lines of "diagonialization failed" or "potential shift at maximum", which gives them no indication on what to do.
Maybe we could shift the film during the postprocessing of the inp.xml-reading.