Remove per-group settings for now

This drops Layer height as a setting that can be changed per-object but
makes per-object settings work correctly.

Contributes to CURA-255

plugins/CuraEngineBackend/StartSliceJob.py

@@ -86,10 +86,6 @@ class StartSliceJob(Job):
 
                 Job.yieldThread()
 
-            # Hack to add per-object settings also to the "MeshGroup" in CuraEngine
-            # We really should come up with a better solution for this.
-            self._handlePerObjectSettings(group[0], group_message)
-
         Logger.log("d", "Sending data to engine for slicing.")
         self._socket.sendMessage(slice_message)