Refactor database seeds file, and ignore weekends.

Previously, Notifsta would send notifications on weekends. This commit
tests whether it's the weekend, and if so, does not send notifications
anymore (since Hugh's doesn't have lunch / dinner on weekends).

Seeding the database is now also faster, since common functions have
been refactored out of the date loop. Descriptions have also been
removed, since there aren't space in the notification for them.
Change database seed start date.