Review nexus reading

[tkittel]

Review of the file: https://github.com/mccode-dev/McStasToX/blob/main/mcstastox/ReadNeXus.py

This reads McStas generated NeXus files and makes the entries / data available to the interface class. The main purpose of having this layer is that changes in the NeXus file format could impact this file, but hopefully not the interface layer.

The contained class can have settings based on the McStas version contained in the NeXus file, as the way to get certain information may change.