[FEAT] Don't trigger panning with the right mouse button

[tbouffard]

Is your feature request related to a problem? Please describe.
The initial implementation also allows to trigger the panning by clicking the right button (supported by default by mxGraph).
This is an unusual way for panning and this currently displays the context menu which is a strange behaviour.

Example when using the A.2.0 miwg-test-suite file on Firefox 81.0 (French Language)

Describe the solution you'd like
Only trigger the panning with the mouse left button

Additional context
Implementing this will avoid any side effect in the future if want to assign special action to the right button (custom context menu for intance)

[tbouffard]

I have tried disabling the right button support with the following but I have seen no effect (mxgraph@4.1.0)

this.graph.panningHandler.usePopupTrigger = false; // only use the left button to trigger panning

[tbouffard]

I have tried disabling the right button support with the following but I have seen no effect (mxgraph@4.1.0)

this.graph.panningHandler.usePopupTrigger = false; // only use the left button to trigger panning

This parameter was ignored as we also set ignoreCell to true. See #1003