Refine NMR instrument devices to be more precise

[StroemPhi]

As part of working on #12 it became apparent that some definitions of the NMR devices should be improved to be more precise.

• 'NMR instrument': change "An Instrument which is used to carry out a NMR analysis of some sample." to "A measurement device used to conduct nuclear magnetic resonance (NMR) analysis by measuring NMR signals from a sample and processing the acquired data according to predefined protocols."
• 'cardinal part of NMR instrument': change "A part of an NMR instrument which is cardinally important and hence obligatory and compulsatory for the proper intended function of the instrument." to "A device that is essential for the operation of an NMR instrument, without which the NMR instrument cannot function effectively."
• 'optional part of NMR instrument': change "Part of an NMR instrument which is not cardinally important and hence optional / facultative for the proper intended function of the instrument."to "A device that contributes to the functionality of an NMR instrument but is not essential for its basic operation, allowing for enhanced capabilities or specialized analyses."
• tbd [all the other devices and their subclasses]