Merge pull request #3 from pgerdt/Fix-activeDialogs-in-Qt5

[alarms] Fix Qt5 version of AlarmHandlerInterface::activeDialogs()
[alarms] Update alarm enabled status when alarms are triggered

Connect to timed signal alarm_triggers_changed, which lists
the currently active alarm trigger times. Update alarm
enabled status based on which alarms are active.

The processing of the information provided by timed is delayed
500 ms as timed may emit alarm_triggers_changed signals in
rapid succession.
[alarms] Add support for countdown alarms