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/UserInterface/RiuPlotMainWindowTools.cpp

@@ -94,7 +94,6 @@ void RiuPlotMainWindowTools::refreshToolbars()
 
         if ( mpw )
         {
-            mpw->updateSummaryPlotToolBar();
             mpw->updateWellLogPlotToolBar();
             mpw->updateMultiPlotToolBar();
         }