network animator based on Qt4 working with ns-3

 NetAnim currently animates the simulation using an XML trace
 file collected during simulation.
 .
 Using NetAnim is a two-step process:
   - Generate the animation XML trace file during simulation
     using "ns3::AnimationInterface" in the ns-3 code base
   - Load the XML trace file generated in Step 1 with the
     offline animator (NetAnim).