Don't depend on a specific model type here.
Prepare the internal storage to hold other QObject-based timers as well.
Prepare for handling QQmlTimer in TimerInfo.
Support QQmlTimer.
Compress changed signals for object-based timers as well.

Timers with intervals less than one second otherwise make the data very
hard to read, and could create way too many messages on slower systems.
Show the correct timer state for QQmlTimers.
Better default column sizes.
Remove obsolete update timer.