Simple scheduling domain functions.
Find when to schedule a specific poll.
Refine naming.
Check upcoming doesn't count today.
Create method for rescheduling scripts.
Use the new scheduling code instead of the old methods.
Pass scripts around rather than digging it out of a ScriptProgress object repeatedly.
Test function that works out whether to reschedule a complete script.
Test that normal polls will be rescheduled.
Don't reschedule blacklisted connections.
Schedule all polls for a connection, and delete reschedule_monthly_script()
as it's convoluted and unsafe.