Make touchpads and touch-screens usable for navigating the 3D view (with patch inside)

Hi all,

The following patch enables the following behavior:
* if the mouse drag happens after a previous click with the left mouse button (i.e. a "double click mouse drag"), it will pan instead of rotating;
* panning will also be done instead of rotation if the CTRL button is held down while dragging with the left mouse button.

This enables panning with the mouse-pad or on a touch screen, which is impossible otherwise on some device/OS combinations without sacrificing other useful functionality. Normal mouse operation should not be affected (much) by this addition.

On a touch-screen panning will happen after quick succession of a touch and a drag. With the mouse-pad the preferred way is to hold CTRL down while dragging, but a double-click (two taps) followed quickly (almost like a triple-tap) by a mouse drag will also trigger panning instead of zooming.

I used the CTRL button instead of SHIFT (some other CAD programs do that), because on Windows pressing SHIFT a few times will trigger Sticky keys, while the CTRL key won't have any such effect.

Patch is included here:

[double_click_drag_means_pan.patch](https://github.com/CadQuery/CQ-editor/files/13697839/double_click_drag_means_pan.patch)

Hope it helps !

Cheers,
Csaba