Updated doc strings & removed mc version of 2op1t

Also:
-changed some instances tlist to taulist for clarification
-changed normalized correlation functions to steady state only

I made a noticed a few mistakes in the docstrings and now I think all the inconsistencies are fixed.

Re the mc correlator:

It looks to me like the quantum regression theorem was attempted to be applied here but the initial condition requires a density matrix. However, the MC method only takes an initial condition as a state so this would not work in general. I suppose in principle there could be special cases that work, but I think the MC correlator needs a different technique.
I thought about this for awhile and found it a bit inconsistent to return both because g1 only makes sense for stationary statistics but G1 can be for any statistics. I can certainly put that back but it does seem more consistent to me to only return g1/2.