Dftbplus-step

* Updated the code to work with the latest installer. In the process, directly
incorporated the Slater-Koster files in the release because their location at
dftb.org changed, causing errors in the installation.
* Add tracking of timing for calculations to ~/.seamm.d/timing/dftbplus.csv for
analysis and future use in prediciting job limits for queueing systems.

* Fixed issue with periodic cells with symmetry and primitive cells that caused
problems with e.g. charges and spins.
* Added RMSD and displacement between initial and final structure in optimization.
* Added to output and put key results in tables to make easier to read.

* Logging at the INFO level made the output from geomTRIC too verbose. Changed to
DEBUG level.

* The code had several errors to do with detecting whether the calculation was
spin-polarized or not. This has been fixed and the detection simplified.

* Added the standard results -- energy, gradients, and model -- that can be written
to Results.json for drivers like Structure Step and Thermochemistry Step.