* Rudimentary fix to make side_by_side stereo work in master

* Fix Triton asset file
 * Display an error if no Property matches a regex in setPropertyValue
 * Correct user-facing name for some Moon assets
 * Add fade in and fade out helping functions
 * Reenable label fading in New Horizons
 * Added GUI hint to hide uninteresting nodes
 * Set Hidden Hint on barycenter nodes

include/openspace/scene/scenegraphnode.h

@@ -137,6 +137,7 @@ public:
     Renderable* renderable();
 
     const std::string& guiPath() const;
+    bool hasGuiHintHidden() const;
 
     static documentation::Documentation Documentation();
 
@@ -152,6 +153,10 @@ private:
     std::vector<SceneGraphNode*> _dependentNodes;
     Scene* _scene;
 
+    // If this value is 'true' GUIs are asked to hide this node from collections, as it
+    // might be a node that is not very interesting (for example barycenters)
+    bool _guiHintHidden = false;
+
     PerformanceRecord _performanceRecord;
 
     std::unique_ptr<Renderable> _renderable;