Clean up

[pmer]

• Fixes some errors and warnings in my IDE.
• Adds PyLint linter.
• Adds Black code formatter.
  • Enforces a line length of 120 characters.
• Improves static analysis for some things.

Soon we can enable a CI to run PyLint and Black on pushes. One day we might be able to look at running MyPy on the core files.