Second round of review fixes for the silence-after setting.
A fire now clears any stale ringingSince before it re-resolves the slot.
Before, the resolver's new one-shot close could switch off, or delete, the
very alarm that was about to ring.
A one-shot alarm displaced by another alarm's fire is switched off, as on
every other close of an undismissed cycle, instead of being armed for the
same time tomorrow.
onAutoSilence, onSilenceAfterChanged and the reboot resume now share one
rule. A ring still inside the window has its backstop re-armed, measured
from when it started, or from now if the clock has moved back behind that
start, so a clock change cannot stretch a ring past one window.
Refs #17
makiolaj
fb875ca71c