issue94RadiopharmView - Add a minimal view for nuclear medicine

This PR adds a “complete” minimal view for nuclear medicine to openrem. It’s complete in the sense of being functional and implementing every required page/functionality, (with the exception of export buttons, which at the moment raise not implemented exceptions) however most parts of the view don’t actually show much data specific to nuclear medicine (e.g. the detail page and the summary page), though a few nm-specific charts already exist.

The PR is done now already, to keep the changes at an at least somewhat reasonable level, with the intention of using it as a base on which specific additions for nm can be done. (Like extending the summary and detail view, implementing the export and providing more charts)

I took the liberty to combine some code duplications in the views.py file into small helper functions.