Add helper that reads Result definition from results folder

[janvonrickenbach]

And converter that computes the Composites files from the result definition.

[janvonrickenbach]

Think whether we want to have a CompositeModel class. It could have a constructor with only a path as an argument (or a result definition).
It would contain the relevant operators (LayupOperators), the different providers, an already enriched mesh and the result definition. We could also add the sampling point and composite failure operators, but I'm not sure it is a good idea.

[roosre]

Composite Model and Result Definition should both have a constructor with a json as input.