Resolve issue: https://github.com/kanaka/noVNC/pull/101

Based on proposal from @mightpenguin:
Matthew Balman <emperor@mightypenguin.org>

If view_only option is set then do not send mouse and keyboard events.
This is not a secure/enforced way to make a client view only. To
enforce view only at the server, most VNC servers support setting
a view only password.