[Core] delete plugin instances on app exit
[DBusManager] qt5-compatibility
[DeadLyrics] qt5-compatibility
[DevMon] qt5-compatibility
[Dolozhee] qt5-compatibility
[HistoryHolder] qt5-compatibility
[DumBeep] qt5-compatibility
[Glance] qt5-compatibility
[HotStreams] qt5-compatibility
[KNowHow] qt5-compatibility