Added SSH.NET

Added project SSH.NET (Renci.SshNet) from
https://sshnet.codeplex.com/releases/view/120504 for SSH support.
Signing for the assembly is disabled because I don't own the key.
SSH implementation is for the future purpose of controlling a HDMI-CEC
compatible device via LAN.
E.g. the Raspberry Pi supports HDMI-CEC via libcec so that it can be
used to control the TV via network.