Remove atomate dependence from emmet-cli / charge density analysis improvements

[esoteric-ephemera]

Fully removes the atomate dependence from emmet-cli. VaspDrone has been replaced with TaskDoc.from_directory, and the VaspCalcDb has been replaced with a TaskStore object that repurposes only its core internals.

Also adds ability to parse existing bader / ddec6 charge density analysis files during TaskDoc creation / CLI parsing. Should save some time if these are precomputed and stored.