Feature/asset meta update part2 (#1855)

* changes to asset/loader/meta to support adding nodes created at runtime

* update assets meta.

* update tle helper and gui to work with changes

* fixes #1840

* group titan trail and atmosphere with globe

* license for magnetosphere

Co-authored-by: ElonOlsson <olssonelon@gmail.com>

include/openspace/scene/asset.h

@@ -117,6 +117,13 @@ public:
      */
     void setSynchronizationStateRejected();
 
+
+    /**
+     * Register a SceneGraphNodeIdentifier with the asset
+     * (used to associate Nodes with asset meta)
+     */
+    void addIdentifier(std::string identifier);
+
     /**
      * If the asset has not yet been loaded, this function loads the asset and returns the
      * success state. If the loading succeeded, the Asset transitions into the \c Loaded