Support the PLAIN (and/or other) authentication method in the proton-j messenger

The proton-j messenger only supports anonymous authentication at the moment. Lack of other mechanisms limits the messenger's usability especially with message brokers.

A simple test is running the org.apache.qpid.proton.example Recv and Send classes against the Qpid java broker. They work only if the AMQP port uses anonymous authentication. With the default password file authentication they fire a steady stream of exceptions like:

Sep 04, 2013 4:21:06 PM org.apache.qpid.proton.messenger.impl.MessengerImpl processActive
SEVERE: Error processing connection
java.io.IOException: An established connection was aborted by the software in your host machine
at sun.nio.ch.SocketDispatcher.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(Unknown Source)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(Unknown Source)
at sun.nio.ch.IOUtil.read(Unknown Source)
at sun.nio.ch.SocketChannelImpl.read(Unknown Source)
at org.apache.qpid.proton.driver.impl.ConnectorImpl.read(ConnectorImpl.java:127)
at org.apache.qpid.proton.driver.impl.ConnectorImpl.process(ConnectorImpl.java:93)
at org.apache.qpid.proton.messenger.impl.MessengerImpl.processActive(MessengerImpl.java:502)
at org.apache.qpid.proton.messenger.impl.MessengerImpl.waitUntil(MessengerImpl.java:617)
at org.apache.qpid.proton.messenger.impl.MessengerImpl.waitUntil(MessengerImpl.java:585)
at org.apache.qpid.proton.messenger.impl.MessengerImpl.recv(MessengerImpl.java:254)
at org.apache.qpid.proton.messenger.impl.MessengerImpl.recv(MessengerImpl.java:259)
at org.apache.qpid.proton.example.Recv.run(Recv.java:108)
at org.apache.qpid.proton.example.Recv.main(Recv.java:127)