- added a new global setting only accessible through the Tcl Shell,

named: global_mouse_pan_button
It can be set through set_sys TclCommand or the value getted through
get_sys TclCommand.
Values are 1 for left mouse button, 2 for middle mouse button and
3 for right mouse button.
It does hurt my hand (wrist) keeping the middle mouse button pressed
when panning and I very much preffer panning with RMB.
The default setting is pan_button = middle mouse button.

PlotCanvas.py

@@ -445,7 +445,7 @@ class PlotCanvas(QtCore.QObject):
     def on_mouse_press(self, event):
 
         # Check for middle mouse button press
-        if event.button == 2:
+        if event.button == self.app.mouse_pan_button:
 
             # Prepare axes for pan (using 'matplotlib' pan function)
             self.pan_axes = []
@@ -461,7 +461,7 @@ class PlotCanvas(QtCore.QObject):
     def on_mouse_release(self, event):
 
         # Check for middle mouse button release to complete pan procedure
-        if event.button == 2:
+        if event.button == self.app.mouse_pan_button:
             for a in self.pan_axes:
                 a.end_pan()