Oxo handling

[mgt16-LANL]

This branch adds additional handling for OXO-bound complexes.

OXO ligand compounds are particularly relevant for actinides and catalytic water-based systems.

This change adds 4 basic functionalities:

1. Change logic of handling oxos to force trans oxos by default for only actinide systems with the option to turn this off.
2. Add tabulated experimental metal-oxo distances and enable setting of average experimental distance for oxos.
3. Enable 'ff_preopt' for oxos and keywords options allowing for cleaning more crowded ligands around metal-oxo centers.
4. Allow (though not recommended) for 'override_oxo_opt' to still perform XTB or UFF optimization of fully build molecules with oxos.

If you are running actinides with oxos - the following parameters are suggested for MOST cases:
parameters = { 'force_trans_oxos':True,
'ff_preopt':True,
'override_oxo_opt':False}