Fix accounting for NAT nodes in the Clearinghouse #147

The current Clearinghouse includes code to use Affix for working with nodes that are behind NAT gateways or firewalls, but the accounting/vessel selection functions were not updated. At the moment, the clearinghouse code erroneously assumes that NATted nodes have a prefix of "NAT$" to their node names. Since this is not the case with the latest nodemanager, the clearinghouse will assume it controls no NATted nodes.

With the latest nmmain, nodes will not use IP addresses anymore, but opaque hex-strings as identifiers. The clearinghouse will need to look up the identifier and port number on the advertise services and find out what the Affix string to contact the node is (if any). It can only recognize a NATted node then, because such node will use the TCPRelayAffix (or the future TransparentTCPRelayAffix).