[Plot] Begin integrating with telemetry handler

Miscellaneous tweaks and fixes to begin showing merged
real-time and historical telemetry, WTD-806.

platform/features/plot/src/elements/PlotSeriesWindow.js

@@ -41,5 +41,7 @@ define(
                 }
             };
         }
+
+        return PlotSeriesWindow;
     }
 );