Wp 850 fix messagehandler infinite msg loop

Fix infinite message loop where the MessageHandler on a PZP would forward msgs for a previously connected WRT to the PZH and receive them again ad infinitum.

Also clean up the MessageHandler by removing unused code, refactoring some duplicated code and rename some functions so it's more obvious what they do. 

Jira-issue: [WP-851](http://jira.webinos.org/browse/WP-851)