Homestyx hydra

R1:2d7f574b9d6d

Allow Calendar imports to be configured with hourly or daily auto-updates

Summary:
Ref T10747. For URI-based (and, in the future, Google-based) imports, we can automatically refresh them periodically.

(In the general case there's no way to get a push notification for an ICS file, so we just have to do this every-so-often.)

Test Plan:
- Set an ICS file to update hourly.
- Used `bin/trigger fire --id ...` to fire it artificially.
- Saw Calendar update.

Reviewers: chad

Reviewed By: chad

Maniphest…
Repository: R1 hydra
Commit Date: Oct 26 2016