LightBoxCanvas zax can be specified with 0, 1, 2, or any of 'xyzXYZ'

fsl/fsleyes/displaycontext/canvasopts.py

@@ -58,7 +58,8 @@ class SliceCanvasOpts(props.HasProperties):
     """
  
 
-    zax = props.Choice((0, 1, 2))
+    zax = props.Choice((0, 1, 2),
+                       alternates=[['x', 'X'], ['y', 'Y'], ['z', 'Z']])
     """The display coordinate system axis to be used as the screen *depth*
     axis.
     """