Refactor some larch processes to fit ewokscore.

overview

fix #55 (closed)

• rework larch processes to be closer to ewoks task 'spirit'
• handle modifications done in larch (some properties have been removed so some plot / curves have been removed from plotting)

questions

@denolf with this MR and the previously merged one it looks like we can run the BM23 workflow. Is the refactoring of the XasObject a priority compare to other thinks ? Anyway I will first do another PR removing some unnecessary processing now that ewoks has been integrated.