Code review comment for lp:~tomasgroth/openlp/mupdf

Fixed for PEP8 compliance and trunk-conflicts.
Changed the way the serviceitem was copied/converted in messengerlistener.startup() to make it simpler and removed changes from service_item.
The serviceitem of PDF is a presentation-serviceitem containing a PDF file (in the same way a presentation-serviceitem contains ppt-file), and it remains like this when in the mediamanager or the servicemanager. When going to preview/live-mode the serviceitem is converted to a image-serviceitem and displayed as such. Where in the code the serviceitem-conversion should be done is open for debate. Since it (at the moment) is tied to the Pdf-presentation, maybe it should be a method in the PdfDocument class