Consolidate/update parameter use in GMML

[gitoliver]

In gmml/dat we have multiple copies of the same prep file i.e:
CurrentParams/leaprc_GLYCAM_06j-1_2014-03-14/GLYCAM_06j-1.prep
prep/GLYCAM_06j-1.prep
We need to decide on how to best store and keep these parameters up to date.

Lachele: I greatly prefer lib/off to prep. That format has its own headaches, but they are easier headaches.
We could also consider, say, mmcif.
Ideally, I would like a format that is:
Reasonably easy to understand. (lib/off is nowhere near as bad a prep, which lets you think you understand)
Self documenting (lib/off does this, if tersely).
Allows for details about "if connected to a residue of type X, then apply these geometries to these linking atome"
Extensible, since few do that last one well, if at all.
If deleting atom Y, then adjust charges/geometries/etc., according to these rules.

[gitoliver]

Review in Feb 2022.