Using Apache HTTP-Client instead of basic java URLConnection for Embedder Connection.

Json Requests are working now. However, two issues arrised:
- OVX-Embedder returns code 400, message Bad request syntax ('POST no file HTTP/1.1')
- OVX can not hand two tenant networks over to one Floodlight Controller.
  -> possible Fix: Flush Controller and reassign whole tenant network.

CITMASTER-33 - Finish Integrated Controllers