Add summary multi plot

Improve robustness related to update of Summary Plot Manager

Add RimSummaryMultiPlot
Move shared code into RiaSummaryStringTools
Added "Create Summary Multi Plot" to menu of MultiPlot in project tree

ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp

@@ -134,6 +134,10 @@ void RiuPlotMainWindow::initializeGuiNewProjectLoaded()
     auto sumPlotManager = dynamic_cast<RimSummaryPlotManager*>( m_summaryPlotManager.get() );
     if ( sumPlotManager )
     {
+        auto* obj = RiaSummaryTools::summaryCaseMainCollection();
+        obj->dataSourceHasChanged.connect( sumPlotManager, &RimSummaryPlotManager::onSummaryDataSourceHasChanged );
+
+        sumPlotManager->resetDataSourceSelection();
         sumPlotManager->updateConnectedEditors();
     }