Add sample class

[ka-sarthak]

The need for a Sample class emerges when multiple samples are cut from a bulk material, each treated as a separate entity. These samples have the same material system but can have different geometry and sample IDs assigned.

The Sample class should allow the reuse of a material system (a composite system itself) for multiple sample entries via reference.

Sample also inherits composite system, and reference to its material system is made in the components using a SystemComponent.

Sample(CompositeSystem):
  geometry = Geometry
  components = list[SystemComponent(reference=CompositeSystem)]

[hampusnasstrom]

I think CompositeSystem is already the class you are looking for.

[ka-sarthak]

I summarized our discussions from today in the PR: #82 (comment)