Gpescia/continuous support

Created by: gpescia

Hi everyone,

I added the continuous Hilbert as discussed with signature nk.hilbert.Particles(N=10, L=(3,3,3), pbc=(True,True,False),type="boson"). Additionally there is an implementation of random_state(): For all directions where there are periodic boundary conditions I initialize the particle positions evenly between 0 and L and give them a Gaussian noise. For all directions where there are no boundaries, the positions are initialized with a Gaussian. Please comment on this if you have better ideas for initialization.

I also added a rule for the MetropolisSampler. The rule takes the old positions and proposes a new position for each particle position according to a Gaussian distribution. If there are periodic boundary conditions I take the new positions modulus L (the extend in that spatial direction) and otherwise no modulus operation is done.