R1:f64ca87bfea0

Implement open() and closed() Maniphest tokenizer status functions, plus cleanup

Summary:
Ref T4100.

- Make it easy to choose all open or closed tasks.
- Make "special" tokenizers composable.
- Get `viewer()` generating documentation properly.

Test Plan:
- Ran queries with new tokens.
- Browsed new tokens.
- Viewed docs on new tokens.
- Used plain status tokens.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: chad, epriestley

Maniphest Tasks: T4100

Differential Revision: https…