#353 implement resume and step code
#353 visualise the stopped breakpoint nodes so you can see the nodes being stepped through; or when a breakpoint is activated
#353 first cut of showing the messages at the current breakpoint - not quite working yet mind you ;)
#353 detail view of message working
#353 use less screen real estate for the buttons
#353 use an easier to debug route which changes the payload and adds a header
#353 mostly working debugger - yay! :)
#353 remember if we have to close the detail view due to resuming - so we can reopen it again
#353 use an empty row object when we resume if we're showing the detail view; so we can keep the headers table expanded as we step / resume
#353 update the diagram selection with the last stopped node
#353 double clicking the node now toggles breakpoint setting
#353 nicer looking button toolbar layout