Added minimal example of WIP on separately modeled control plane network.

This script does not actually work at this point (i.e. POX does not
receive control traffic)
Script now kills instances of the default Mininet controller.
Log analyzing script now records flow tracker network and processing times.
Flow tracker new records load on each switch, and mininet_multicast_pox now processes this value when generating logs.
Moved code that could be shared by multiple test routines to groupflow_shared.py.

Also added a new directory to the groupflow_script folder to make it
clear which scripts are non-functional works in progress.