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)

mainwindow.h

@@ -98,6 +98,7 @@ private slots:
     void filterSetAll();
     void filterClearAll();
     void headerClicked (int logicalIndex);
+    void DBCSettingsUpdated();
 
 public slots:
     void gotFrames(int);