added a name field to Sender, which is now used as a hash key

Node: changed list of Senders to hashtable of Senders using a string as
a key
added ConnectionInformation message; this will be sent by a node
instantiating a connection to convey important information to the
receiver
added sending of ConnectionInformation message to Client when connecting

added handling of ConnectionInformation message to Registry

made IP addresses being passed around between classes agree
(MessagingNode's get local ip method was returning the incorrect value;
now all IP addresses are calculated via the sockets themselves)

added toString to ConnectionInformation and made a tiny tweak to
toString of RegisterRequest
synchronizing methods which ought to have been already
created RegisterResponse