Merge branch '15.06'

* 15.06:
  Also add the parent class' command line arguments
  Only process the layer data if the layer view is active.
  Write to the correct variable so bed temperature is properly updated
  Correct a copy-paste error in getConnectionList
  Properly close all open USB connections on shut down
  Catch errors when trying to close the connection thread
  Enlarge the zone where you can use scrolling to look trough the layer mode.
  tiniest detail concerning the padding of the layer count label
  Adds layer count

cura/CuraApplication.py

@@ -110,6 +110,7 @@ class CuraApplication(QtApplication):
         self._plugin_registry.loadPlugin("CuraEngineBackend")
 
     def addCommandLineOptions(self, parser):
+        super().addCommandLineOptions(parser)
         parser.add_argument("file", nargs="*", help="Files to load after starting the application.")
 
     def run(self):