Adds a communicator which does not provide communication to the
guest machine. All methods for the communicator are simply stubbed
with a successful result. This allows a guest to be configured
with the `:none` communicator and Vagrant to properly `up` it.
This currently lacks any user notification or guards within
configuration to verify guest configuration does not rely on
the communicator. It is wrapped as experimental to allow early
access to the basic functionality without making it generally
available.
