raise warnings in MetropolisHamiltonian if the Hilbert!=operator.hilbert

Created by: PhilipVinc

I just finished hunting down why my code was throwing mysterious numba exceptions. well. Here it is. I had an operator in doubled Hilbert space sampling the diagonal of a density matrix, but didn't realise.

This simply makes the sampler throw informative messages if this happens. Saving sanity to poor users. Amen