Fixed background color setting for legends and refactored Legend class hierarchy

* Added a new cafTitledOverlayFrame as a base-class for all ResInsight legend classes
  * Inherits cvf::OverlayItem

ApplicationCode/ProjectDataModel/Rim2dIntersectionView.cpp

@@ -573,7 +573,7 @@ void Rim2dIntersectionView::updateLegends()
     RimGeoMechView * geoView = nullptr;
     m_intersection->firstAncestorOrThisOfType(geoView);
 
-    cvf::OverlayItem* legend = nullptr;
+    caf::TitledOverlayFrame* legend = nullptr;
 
     if (eclView)
     {

ApplicationCode/ProjectDataModel/RimLegendConfig.cpp

@@ -32,6 +32,7 @@
 #include "RimStimPlanColors.h"
 #include "RimViewLinker.h"
 
+#include "cafTitledOverlayFrame.h"
 #include "cafCategoryLegend.h"
 #include "cafCategoryMapper.h"
 #include "cafOverlayScalarMapperLegend.h"
@@ -675,7 +676,7 @@ void RimLegendConfig::setTitle(const QString& title)
 //--------------------------------------------------------------------------------------------------
 /// 
 //--------------------------------------------------------------------------------------------------
-cvf::OverlayItem* RimLegendConfig::legend()
+caf::TitledOverlayFrame* RimLegendConfig::legend()
 {
     if (m_currentScalarMapper == m_categoryMapper)
     {

ApplicationCode/ProjectDataModel/RimLegendConfig.h

@@ -41,6 +41,7 @@ namespace cvf
 
 namespace caf
 {
+    class TitledOverlayFrame;
     class CategoryLegend;
     class CategoryMapper;
     class OverlayScalarMapperLegend;
@@ -119,7 +120,7 @@ public:
     void                                        setUiValuesFromLegendConfig(const RimLegendConfig* otherLegendConfig);
 
     cvf::ScalarMapper*                          scalarMapper() { return m_currentScalarMapper.p(); }
-    cvf::OverlayItem*                           legend();
+    caf::TitledOverlayFrame*                        legend();
 
 protected:
     virtual void                                fieldChangedByUi(const caf::PdmFieldHandle* changedField, const QVariant& oldValue, const QVariant& newValue);