Create widget for providing thermo for adsorbates

[cfgoldsmith]

Motivation

I like the RMG web interface to provide thermo for a species, given the ChemGraph. It would be good to provide something similar for adsorbates.

Desired Solution

The user provides a ChemGraph of the adsorbate and then either (i) the metal, or (ii) the binding energy of the adatom (for linear scaling relations).

Justification

Some folks may still want to build microkinetic mechanisms by hand. That's fine. We could/should at least make it easy for them to get adsorbate thermo, so that they don't do something silly like explicit fwd/rev reactions that violate thermodynamic consistency.