FIX: sesolve average states (#1115)
FIX: sesolve average states (#1115)

* fix avg states

* Safety check msg tidyup.

* Codeclimate suggestion fixes.

* swap some ValueErrors for TypeErrors.

* underlying cause passed on in StochasticSolverOptions.__init__() checking exceptions

* traj_states saved in result object

cgranade/qutip,qutip/qutip,qutip/qutip,cgranade/qutip