Multisite observables

[yomichi]

Three or more site observables are now available (only what are represented by direct product of one site operators, e.g. SzSzSzSz)

For example, SzSzSzSz on a square plaquette is specified as follows:

[[observable.multisite]]
name = "SzSzSzSz"
group = 0
multisites = """
0 1 0 0 1 1 1
1 1 0 0 1 1 1
2 1 0 0 1 1 1
3 1 0 0 1 1 1
"""
ops = [0, 0, 0, 0]

The result is saved into multisite_obs_#.dat where # is the number of sites on which the operator acts. The format of this is similar to that of twosite_obs.dat.