Mac code signing script and DMG background image

Qt frameworks are not packaged correctly (upstream bug) for Apple's codesign utility to sign them as a framework bundle. So any app containing them cannot be signed either. The changes to the code signing script copy the needed files into place in the owncloud.app bundle before running the codesign tool with --deep so it recursively signs all frameworks and plugins as well as the app itself.
The icons sizes have been increased and the positions altered. The background image now has white boxes to appear behind the icons to avoid the black text of the icon names on the dark background.