[WIP]Trajectory -> Gaussview readable ".log" file

[benrich37]

From #4420

Summary

Major changes:

• feature 1: Adds the class function core.trajectory.Trajectory.write_Gaussian_log, which writes a Gaussview readable ".log" file from the contents of a Trajectory object
  -- Allows mapping site properties to implemented Gaussian properties through the site_property_map argument
  --- Keys for implemented Gaussian properties stored in core.trajectory as constants with name format gview_<property>_key
  --- Currently implements mapping to
  ---- Mulliken (list[float])
  ---- ESP (list[float])
  ---- NBO (list[float])

Todos

• feature 1:
  -- Testing
  --- Making sure log files can be written without error
  --- Since Gaussview is a licensed product, (I believe) it cannot be booted up virtually to test if the produced files are actually readable. However, io.gaussian.GaussianOutput._parse could help us out here.

[benrich37]

@shyuep For core.trajectory.Trajectory.write_Gaussian_log, a handful of helper functions are required - right now they're being held in core.trajectory and are being made "private", but I wanted to check with you if that is okay or if there is another location to hold them in that would make more sense.

There are also some str constants being held in core.trajectory that are supposed to be used by the user for creating custom site_property_map for core.trajectory.Trajectory.write_Gaussian_log - is this overly complicated? It also feels silly to have them defined in core.trajectory, but I'm not sure where I would move them.

[shyuep]

Sorry for the late response. Yes, what you propose is fine. However, we have moved this to pymatgen-core. Please resubmit a PR there when ready.