Encryption

[feschber]

encrypt traffic through dtls using the webrtc dtls implementation (#104)

Todos

• [x] ~Sign certificates using the server (CA = Server?) instead of selfsigned certs.~ Implement fingerprint based authenticity verification
• [x] Properly close unresponsive connections
• [x] Release capture when remote host is not responding to pings
• [x] Release capture, when a new client connects
• [x] Only send input events when the connection is acknowledged
• [x] Release keys, when client does not send pings
• [ ] implement cursor leave logic for one-way control
• [ ] Reinstantiate support for changing ports
• [x] save authenticated keys in config file