[Bug/Question]: Off-Momentum RDT/CRDT calculation

[JoschD]

Bug Description

I found a bug where the (C)RDT calculation fails when analysing either purely off-momentum files, or both on- and off- momentum files together.
The reason is, that it is hard-coded to take the phase model values only from on-momentum files, but the phase measurement values from all files.

This either leads to an error when only off-momentum files are analysed, as no model files can be found,
or to a dimension mismatch later on when both on- and off-momentum files are analysed.

I have now implemented a simple switch in #455 that only takes on-momentum files for both, model and measurement.
I.e. we forbid (C)RDT analysis for off-momentum files (raises error) and ignore off-momentum files when doing a combined analysis (only uses on-momentum files to calculate (C)RDTs).

Is this the behaviour we want, or would it make sense to include all, on- and off-momentum in the analysis?

This question goes out to @mihofer @fscarlier @emaclean @rogeliotomas and @Mael-Le-Garrec

[JoschD]

After discussion with Ewen: Use all files, but warn user that he is using off-momentum files for RDT calculation.