Summary:
Ref T10537. Some sources (like the future "GitHub Repository" source) need to poll remotes.
- Provide a mechanism for sources to emit import cursors.
- Hook them into the trigger daemon so they'll fire periodically.
- Provide some storage.
This diff does nothing useful or interesting, and is pure infrastructure.
Test Plan:
- Ran `bin/storage upgrade -f`, no adjustment issues.
- Poked around Nuance.
- Ran the trigger daemon, verified it didn't crash and checked for Nuance stuff to do.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10537
Differential Revision: https://secure.phabricator.com/D15435
