Made VNC threads daemonic so that they die with the main thread. Implemented the vnc_stop functionality. Still need some kind of monitoring system to make sure that VNC sessions close after a period of inactivity.
Cleaned up VNC Proxy/ProxyPipe to be cleaner. Might need to offload them to celery in order to maintain heartbeats as we can not keep vnc_sesions as a global variable across threads. Alternative is to make them self managing.