Wrote navigation tests for managers.

These complement existing navigation tests for wranglers.
Updated TODO.
Implemented Session.last_score_package_path.

Useful in the (<<) and (>>) commands.
Wrote (<<) and (>>) tests for managers.

These complement existing (<<) and (>>) tests for wranglers.
Wrote (b), (h), (s) tests for managers.

These complement existing (b), (h), (s) tests for wranglers.
Wrote (ess) tests.