Gaussian-step

* Now support HF, DFT, MP4, CCD & CCSD, CBS-x, and Gn methods
* Added PBE, PBE-98, PBE0, and HSE06 functionals
* Added analysis of HOMO/LUMO gap energy
* Added plotting of orbitals and densities
* Added otuput of atomic charges and spins, and placing them on the configuration.
* Added ability to control the system/configuration update

* Capturing stdout prevent users from seeing the output during a calculation.
This fixes that.

* Support running the energy or optimization with HF, DFT, MP2 and MP3 though
testing has not yet been thorough.
* The DFT functional supported are at the moment limited.

* Plug-in created using the SEAMM plug-in cookiecutter.