Added a fixed Pint unit and constant file, added CLI command for creating unit conversion data for the GUI, added new React component for changing the units in the ArchiveBrowser.
The CLI command
I added a menu for choosing the units in the ArchiveBrowser. You can either select SI units, atomic units, or a custom selection for a selection of quantities. By default, a custom selection is used (eV instead of Joule, angstrom instead of meter, otherwise default SI units). This can be changed based on what we think is reasonable.