DBC settings and bugfixes

- Changes in DBC file manager are immediately propagated to the main window (frames, filter labeling)
- Prevent DBC file manager from saving settings too often and too early (this also fixes a bug where sometimes the settings of all but the first DBC file are lost)

dbc/dbcloadsavewindow.h

@@ -31,6 +31,9 @@ private slots:
     void matchingCriteriaChanged(int index);
     void newFile();
 
+signals:
+    void updatedDBCSettings();
+
 private:
     Ui::DBCLoadSaveWindow *ui;
     DBCHandler *dbcHandler;