update main TODO

src/main.cpp

@@ -2,6 +2,9 @@
 /*
  * TODO:
  * - impulsive orbital maneuvers
+ * - convert between satellite state vectors and orbital elements
+ * - orbits with nu (true anom at T0) other than 0 degrees
+ * - plane change maneuvers
  * - Hohmman transfer orbits
  * - make an 'overlay' graphic for things like apoapsis, perisapsis, f1, f2,
  *   	flight path