New alarm configuration UI (same as filter UI)

- Looks almost like the filter configuration UI
- Alarms cannot be disabled any longer, the setting can be removed
from AlarmSettings later. Could use a CheckComboBox for that, but alarms
can already be enabled/disabled per stop.
- New class AlarmSettingsList with convenience methods, just like FilterSettingsList.
Could create a base class for those lists of items with names or use a QHash instead.