[ase-users] Merging !269, which splits ase/calculators/vasp.py

[Eric Hermes]

Hello,

I plan on merging !269 shortly. This MR splits the VASP calculator into
two files. The first file, contained in
ase/calculators/vasp/create_input.py, contains only the logic required
to parse arguments to the Vasp calculator and generate input files. The
second file, ase/calculators/vasp/vasp.py, contains all other
functionality.

This *SHOULD NOT* affect users of the Vasp calculator. However, if your
scripts are importing objects from ase.calculators.vasp other than
Vasp, VaspChargeDensity, VaspDos, or xdat2traj, they will likely break.
Moreover, there is a possibility that subtle bugs remain which have not
yet been noticed. Please let me know if any of your scripts break after
this branch is merged in.

Finally, because this branch was created quite some time ago, all
changes that had been made to ase/calculators/vasp.py in the meantime
have been redone manually in the appropriate new VASP-related
calculator files. The changes have been preserved, but the git history
of the original commits implementing those changes will be lost.
Hopefully this is not a serious issue for anyone.

Eric Hermes