Support for customized forcefields and enhanced citations

• Added support for local forcefields files which can either be used directly or included by existing files.
• Added URI handler to support local files
• Added support for BibTex references in forcefield files, and automatically adding citations to the Reference Handler.
• Add 'fragments' section to forcefields for atom-typing via a fragment or entire molecule. This supports using LigParGen for OPLS-AA forcefields.

Added support for tabulated angle parameters

Merge pull request #64 from molssi-seamm/dev

Added tabulated angle potentials

Added support for Buckingham potentials

Merge pull request #63 from molssi-seamm/dev

Added support for Buckingham potentials

Added molecule information for LAMMPS

Added the molecule each atom belongs to, for LAMMPS.

Added handling of OPLS-AA functional form

• Added handling of the OPLS-AA forcefield
• Moved documentation to new MolSSI theme and diátaxis layout
• Cleaned up internal dependencies and workflows for GitHub

Bug fix: error atom typing larger systems

What's Changed

• Fixed bug with atom typing due to limit in matches. by @paulsaxe in #59

Full Changelog: 2022.2.3...2022.5.29

2022.2.3: Merge pull request #58 from molssi-seamm/rdkit

Fixed bug with atom type assignment due to changed order of atoms. In the process, switch to using RDKit directly, which is both more direct and avoids the ordering problem.

Updated to Python 3.8 and 3.9.

Merge pull request #48 from molssi-seamm/dependabot/pip/pillow-8.3.2

Bump pillow from 8.1.2 to 8.3.2

Internal Release

Remove the vestiges of Tk, which weren't used by caused some issues with dependencies.

Internal Release

Preparing for releasing on conda-forge, which required adding some support files to the release.
Also switched to black from yapf and cleaned up the CI for the package.