minor text tidy up
adding sync attr to subassemblies, moved sync related code out of craft and into helper to be used by craft and subassembly. replicated equivilent craft sync tests for subassembly
slight adjustments to transfer_controller and transfer_dialog to allow them to work for both craft and subassemblies.  Both craft and subassemblies can now be moved, copied and set to sync via the interface