Plant explorer launch

[krivard]

Overview

Closes #29.

What did you change in this PR?

• issue checklist (see Fix plant explorer launch blockers #29)
• replaced long-lifetime if/else statements with judicious use of mo.stop
• removed generator filters & related furniture if the plant has only one generator
• minor whitespace opinions

Testing

How did you make sure this worked? How can a reviewer verify this?

Ran locally. Some good test plants:

• CO / Adams / Cherokee for multiple generators where all have generation data available
• WA / King / University of Washington for multiple generators where only a subset have generation data available
• CO / Boulder / Boulder Canyon Hydro (55932) for maximum unavailable data (no plant gen, no generator gen, no generator attributes)
• CO / Boulder / Jack's Solar Garden for single-generator case

To-do list

• Update relevant documentation - like comments, docstrings, README, release notes, etc.
• Review the PR yourself and call out any questions or issues you have

[cmgosnell]

some tinsy suggestions but nothing blocking for me! looks so good!