Refactor schedules to use simpler

* [X] Refactor holidays to use simpler.
* [X] Refactor street sweeping to use simpler.
* [X] Refactor schedules to use simpler.
* [ ] Add tests for street sweeping, holidays, and schedules tasks (Done but commented out, see #27)

This needs to be wrapped with something like `using (Db.Connect()) { }` so that the connection is disposed.