Gui fixes and added fusesource client to jar

I accidently stumbled over your MQTT jmeter plugin and tried it out. It works good after fixing the following 2 little issues.

1. It seems the Fusesource Client is not included in the built jar file, so I added the Maven Shade Plugin to do so
2. Their was a bug in the GUI, because when switching windows the client id and OneConnectionPerTopic fields were emptied