Add solvent notebook to docs

[Gabrielgerez]

In the notebook is an example for a single hydrogen atom, and a "water" molecule consisting of only point charges. There is a bug in the plotting of the simplified water molecule reaction potential. Can be removed without destroying the example. Also, I'm quite sure that this can be readily expanded to a more difficult example, as the reaction potential microiterations do not care for what type of density is fed to them.

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Base: 85.73% // Head: 85.73% // No change to project coverage :thumbsup:

Coverage data is based on head (13373d6) compared to base (b2ec716). Patch has no changes to coverable lines.

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