More flexibility when handling constraints
Based on issue #350
Optimally the translational and rotational constraints should be able to both supply a nullspace before fitting and be able to project solutions afterwards.
The constraints should be subdivided into orders when possible.
The constraint matrices should be accessible based on order in order to be fitted simultaneously.
The sensing matrix should be accessible order-wise as well as with and without constraints imposed already.
There should be a clear mapping between orbits, parameters, constrained parameters and orders.
Contact person: @freeriks