Full consideration of the Nut protocol

[gawindx]

Currently, the implementation of the Nut protocol is incomplete and does not allow to respond to signals sent by the server. This shortcoming can cause, among other things, the non-shutdown of the client station hosting WinNUT when the Nut server requests a forced shutdown of the client (s). Other signals are also not supported and are not mentioned here.

[dylan-kerr]

#100 and #101 partially address this, specifically for the forced shutdown case.