Catenary editor: keep catenary parts out of node editing, pick and drag anchor poles

scene/scenenode.h

@@ -413,6 +413,7 @@ public:
 	bool m_dirty { false };
     bool m_layerhidden { false }; // the node was visible until the editor hid its scenery layer, or the include which defines it
     bool m_preview { false }; // the node was made by the editor to show an include it placed or changed, and is replaced when the include changes
+    bool m_catenary { false }; // a part the catenary assembled (world/catenary_scene.cpp): it's changed by the catenary tool, not edited as a node
     scene::layer_handle m_layer { null_handle }; // scenery layer this node belongs to, if any
     // include of an *.inc template which defines the node; 0 if the node is defined directly by a scenery layer file.
     // such nodes can't be rewritten one by one on scenery save. set only for scenery opened for editing