Use Qt5 syntax for all signals/slots
Review Request #123474 - Created April 23, 2015 and submitted
This patch transforms old signals/slot syntax to the new one one introduced in Qt5. Not sure if this needs review, because everything compiles fine and thanks to the new syntax all issues would be spotted during compilation, but it's a quite a big patch and would be safer to have someone else to review it.
Everything seems to work as before.