List of modified Base Classes and AppDefs

@sanbrock I just made a mock PR from FAIRmat-NFDI:nexus_definitions:fairmat to nexusformat/definitions:main to check which base class and appdef NXDL files where changed:

NXdata
NXaperture
NXsource
NXdetector (unclear)
NXenvironment -> added NXactuator
NXinstrument -> added NXactuator
NXprocess
NXroot
NXsample
NXsample_component
NXsensor
NXtransformations
NXuser -> added NXidentifier

For some of these, the NXDL file has changed quite a bit, but this may just be due to different indentation, formatting, etc., so we should check carefully if the contents have also changed.

FAIRmat-NFDI / nexus_definitions

List of modified Base Classes and AppDefs #240