Chat plugin TLSUtil class changes as suggested from author
 - see https://github.com/freedomotic/freedomotic/commit/1f823869d1a8e9ac12cfec94b51ce76255920e83#plugins-devices-chat-src-main-java-com-freedomotic-plugins-devices-freedomchat-tlsutils-java-P6
first commit of mqtt plugin based on moquette library
some changes to mqtt plugin
renamed mqtt plugin to mqtt-broker
updated moquette lib to 0.6 version - now a configuration file can be passed as parameter
added icons