Refactor interface_reactions module, add support for Plotly

[mattmcdermott]

Summary

• Add: support for Plotly: calling plot() now provides a backend option for choosing matplotlib or Plotly.
• Add:GrandPotentialInterfacialReactivity class to separate code based on the use of grand potential phase diagrams (this greatly decreases the complexity of the __init__ args) and is a more inherited approach in general
• Add: get_dataframe() method for plotting possible reactions in a Pandas dataframe. Users would typically have to write/copy boilerplate code to do this each time
• Fix: Better matplotlib plotting, included annotations
• Fix: Cleaner, more readable code

Checklist

• Code is in the standard Python style. The easiest way to handle this
  is to run the following in the correct sequence on your local machine. Start with running
  black on your new code. This will automatically reformat
  your code to PEP8 conventions and removes most issues. Then run
  pycodestyle, followed by
  flake8.
• Docstrings have been added in the Google docstring format.
  Run pydocstyle on your code.
• Type annotations are highly encouraged. Run mypy to type check your code.
• Tests have been added for any new functionality or bug fixes.
• All linting and tests pass.

[mattmcdermott]

@mkhorton My plan is to have this PR done by Wed, September 8, based on the previous timeline goal we set

[mkhorton]

Fantastic, thank you for the update @mattmcdermott !

[mattmcdermott]

@mkhorton Should be pretty much done. Seems like linting and tests are failing for recent changes related to Optimade.

Note: you'll see I changed something with PDPlotter -- it was an old method I had written called htmlize_formula(). Turns out that method already existed in pymatgen.util.string, so I removed it from PDPlotter and replaced where it was used.

[coveralls]

Coverage decreased (-0.6%) to 83.153% when pulling 8492558 on mattmcdermott:interface_rxns into 2c6ac61 on materialsproject:master.

[mkhorton]

Thanks @mattmcdermott! I think that method is also available on Composition etc. directly (via the Stringify mixin), just an fyi.

[mattmcdermott]

Thanks @mattmcdermott! I think that method is also available on Composition etc. directly (via the Stringify mixin), just an fyi.

Ah true. The only downside is for compositions like Composition("FeO2"), it automatically puts "1" as a subscript:
e.g.,Fe_1 O_2

[mkhorton]

Ah, I guess it acts on the Composition directly rather than formula, fair enough.

[mkhorton]

Merged. Thanks again @mattmcdermott, this is great!