Add classes for simple measurements

[aalbino2]

There are several techniques that are addressed in MOVPE that I am copy-pasting in each user plugin, I would like to place it here.

This would allow also highr visibility of the techniques we started working on.

They contain so far very few metadata. We can indeed keep espanding them more&more

these are the ones:

• AFM
• LightMicroscopy
• Reflectance Spectoscopy
• Hall

For reflectance and hall I would provide a general class, pretty much like the other two, and also the Lakeshore and Laytec specific classes and parsers (in separate plugin but inheriting from these classes)

let me know what's your opinion @hampusnasstrom

@ka-sarthak are you working on some of these already?

[ka-sarthak]

@aalbino2 I do have a use case for PFM, which is a specialization of AFM. I will be working on it in the coming weeks. Btw, it might be a good opportunity to check if your AFM class can be used as a base section for PFM. In general, I do agree that we should move/develop more measurement-related schemas in this repo while making sure they are generic enough.