This stores the alarm state as well as the alarm and snooze time
to gsettings. This alllows us to tell the user about missed alarms.
A user could miss alarms for two reasons:
- Clocks wasn't running when the alarm went of.
- The user didn't stop the alarm within "ring-time"

This also adds the baseline for starting Clocks via systemd user .timer
units by making Clocks checks at startup if any alarms need to go off.

As a side effect: closing Clocks doesn't stop an alarm and when Clocks
is reopend within "ring-time" after an alarm or snooze the alarm starts
ringing again.