Move to TypeScript #1464

The main part of #1448 is to move to TypeScript, but this comes with a lot of things

1. Transcribing JavaScript to TypeScript
2. Importing and using types from 3rd party libraries
3. Simplifying type expressions for tests
4. Bar raising the TypeScript type options to be more strict
5. Bar raise typing
6. Refactor for a cleaner codebase and test harness