for week 1 testing
important improvent, solved the problem on detecting disconnected switches.
a transparent agent
nothing
transparent agent only on tornado
make switch to controller connection into class
removed some old code
adding comments
fixed problems unpacking port status msg
roll back to pure controller & fix bugs
add OFPT_FLOW_MOD into lib & can use flow_modify to add flow
trying to fix issue #1
trying on multi thread
another try on multithread