Summary Multiplot: sync plot selection in tree with view (#8788)

* Make sure the subplot selected in the tree is shown in the multiplot viewer. 
* Clean up multiplot toolbar handling a bit
* Remove old summary plot toolbar.

ApplicationLibCode/Commands/RicCloseSummaryCaseInCollectionFeature.cpp

@@ -96,5 +96,5 @@ void RicCloseSummaryCaseInCollectionFeature::onActionTriggered( bool isChecked )
     }
 
     RiuPlotMainWindow* mainPlotWindow = RiaGuiApplication::instance()->mainPlotWindow();
-    mainPlotWindow->updateSummaryPlotToolBar();
+    mainPlotWindow->updateMultiPlotToolBar();
 }