Support "../" in relative SceneJS.Instance name config

"../" prefixes in Instance node name configs allows upward traversal through namespaces set by Name nodes to locate Symbols defined at higher levels.

   SceneJS.name({name: "foo"},

      SceneJS.symbol({
                 name: "teapot"
             }
,
           SceneJS.objects.teapot()
      ),

      //----------------------------------------------------------
      // Instance the teapot Symbol from inside a namespace
      // within that in which the Symbol is defined.
      // See how the relative symbol reference starts with a "../"
      // to back up one level into the Symbol's namespace.
      //----------------------------------------------------------

      SceneJS.name({name: "bar" },

          SceneJS.instance({name: "../teapot" })))   // Resolves to "/foo/teapot" from within "/foo/bar"