project.get_random_confs_from_states

This PR includes the reincarnation of a project method that samples conformations from a particular MSM. (project.get_random_confs_from_states

It also includes a slight re-write of SaveStructures.py to utilize the above function. Currently the code is all there but I want to test it, to be sure it's doing the right thing. But the tests are slightly broken at the moment...