fix: make infill_mesh visible by default because it's the only setting which is only visible in the per-object settings menu which is not normally visible (CURA-833)

Because it should never show up in the normal global/extruder settings tab, people might forget about this setting. It's one of the reasons per-object settings is awesome ^^.

cura/CuraApplication.py

@@ -233,6 +233,7 @@ class CuraApplication(QtApplication):
             meshfix
             blackmagic
                 print_sequence
+                infill_mesh
                 dual
             experimental
         """.replace("\n", ";").replace(" ", ""))