Setup package

[ka-sarthak]

Building upon the files copied from nomad-measurements in https://github.com/FAIRmat-NFDI/readers-xrd/pull/1, this PR does the following:

• restructuring the package
• adding setup
• removing nomad-related functions
• removing dependency on nomad

Pytests work for readers and utils.

Resolves the issue https://github.com/FAIRmat-NFDI/nomad-measurements/issues/99 @aalbino2 @hampusnasstrom

[ka-sarthak]

@hampusnasstrom

• I checked that the setup works without setup.py. Removed the file.

• nomad.ureg and the registry in fairmat-readers-xrd seem to be consistent: I installed fairmat-readers-xrd in the same venv of nomad-measurements, used the readers in the schema.py from the package. The pytests for schemas seems to work without error.

  So things work for now. maybe because they install the same version of pint. But this can change in future I am afraid. One solution could be not do quantity conversion in the readers, but rather return nested dict with value and units.

I will merge this for now and raise an issue to handle this better.