Add snooze support for calendar reminders (toast UI, service, DB) (#825)

* Filter reminder snooze options by default reminder

* Some updates.

* Fixing empty welcome page issue and attendee loading.

* Icon system for notifications and snooze options etc.

Wino.Core.Domain/Interfaces/IPreferencesService.cs

@@ -222,6 +222,11 @@ public interface IPreferencesService : INotifyPropertyChanged
     /// </summary>
     long DefaultReminderDurationInSeconds { get; set; }
 
+    /// <summary>
+    /// Setting: Default snooze duration in minutes for calendar reminder notifications.
+    /// </summary>
+    int DefaultSnoozeDurationInMinutes { get; set; }
+
     CalendarSettings GetCurrentCalendarSettings();
 
     #endregion