Panning mouse filter cannot be changed in the Zoomer plugin

[ToniMarc1990]

Describe the bug
Unlike the zoom mouse filters, the filter for panning (pressed middle mouse button) cannot be changed. There is no way to change or configure that other than copying the code into my own class and modify it.

It would be good and consistent if that mouse filter can be set. Generally this should apply for all standard Plugins.

[ToniMarc1990]

It look like that #631 already addressed this (although it's not in the latest release).