Defend against evil UI connections

[dnwiebe]

We believe that it might be possible for an evil originating Node to construct a CORES package with a server name of "localhost" or 127.0.0.1 or 0.0.0.0 that might persuade an exit Node's ProxyServer to make a UI connection to its own WebSocketSupervisor and allow the evil originating Node to control the exit Node.

The ProxyClient should be modified so that it rejects any CORES package with a URL containing "localhost", "127.0.0.1", "0.0.0.0", or any other reference to the local machine. When malefactor banning comes on board, this should result in a malefactor ban by wallet of the source.

Also, modify the ProxyServer so that no CORES package can be created, even accidentally, with those hostnames; that way, the ProxyClient can be confident that any originating Node that sends such a CORES package really is a malefactor.

Check out the code and see if it's appropriate to also trigger on the IPv6 versions of those addresses.