added previously missing .classpath, .project, and .settings so that
it's possible to import the project properly on a different machine :/
really messy initial main() for Registry and MessagingNode

changed Client.connectTo() to return the created Sender instead of
adding to the node

added toString() to RegisterRequest for debugging convenience
made Messaging node Runnable; exported all contents of main() except for
command line parsing into run() as it should be

changed startServer() from public to protected in Node
made Registry Runnable and moved contents of main (except for command
line argument parsing) to run()

added missing System.exit() to MessagingNode
created DeregisterRequest
documentation fixes and todos