submodels of msms

[clonker]

Concerns mostly PR #39. Should we introduce the ability to create a MSM submodel directly? This would involve creating a submodel of the associated count matrix if one was provided and re-estimating the transition matrix on a restricted set of states. From my perspective there is one

• pro: easier to use, also markov state models can be submodeled, just as count models

and one

• con: intrdocues a circular dependency between markov state model and markov state model estimator and/or needs further checks whether the restricted model is still at least weaky connected.

[clonker]

opted for states over symbols