Just some name changes and such in mtf_utils.py.
Adding a run file for d+id spin liquid states on triangular lattice in a new directory pyvmc/systems, which could include such run files in the future..
Added function to return average of BCS stats over all lattice sites.
Improved handling of on-site (e.g., chemical potential) terms in the mean-field Hami, and some other basic (assert-related) improvements.