Add isolation list to track tooltips

If a track is hovered when debug mode is on, it will now also show the names of isolated circuits the track belongs to, if any.

scenenode.h

@@ -330,6 +330,7 @@ public:
         export_as_text( std::string &Output ) const;
     std::string const &
         name() const;
+	virtual std::string tooltip() const;
     void
         location( glm::dvec3 const Location );
     glm::dvec3 const &
@@ -379,6 +380,13 @@ basic_node::name() const {
     return m_name;
 }
 
+// Returns the tooltip of this Node when hovered with the mouse cursor.
+inline
+std::string basic_node::tooltip() const
+{
+	return m_name;
+}
+
 inline
 void
 basic_node::location( glm::dvec3 const Location ) {