Fix #130: the user can choose whether to show the axes or not in function set_scene

[hermosaaurora]

In the latest code, the set_scene code can only suppport show_axes=True.
So maybe we can toggle it with the option self.show_axes, just in the function set_scene.
Of course it works if the users manually toggle it False after the function call set_scene, but they may not know about the argument without digging into the code, since when they initialize the Viewer class and call the set_scene function, there are no reminders.