notifications: allow to configure how to sync desktop notifications
Added kcm ui with global and app-specific config options. Global options affect all notifications: - Persistent only? --> Sync only notifications with timeout == 0? - Include body? --> Add body string to summary when syncing? - Minimum urgency Per-application options affect notifications sent by a specific application: - Sync it at all? - If yes, allow to define a "blacklist" pattern (QRegularExpression) to define which notifications should *not* be synced. Applications are maintained in the per-device config and added when seen the first time by the notification listener. From that moment on they can be configured in the kcm ui.