* fixed an issue that lead to a crash in case the sound file for a notification could not be accessed
* removed infinite duration of notification in favor of notification pinning
* allow particular notifictions to be pinnned to the desktop by using announcements directly as they are announced (this allows for certain critical notifications to stick to the screen permamently until the user closes them)
* announcements now reference applications by name instead of by ID, this is more convenient because the application name is displayed in the gotify interface such that it is easy to create announcement hooks for particular notifications