Use scroll for moving the chart, not zooming it

[olekscode]

At the moment, we use scroll to zoom-in and zoom-out. And we use mouse drag-n-drop for moving.
To be consistent with OS (and browsers), I suggest to use horizontal and vertical scrolls for moving and use "Pinch-to-zoom" (like on smartphone) to zoom-in and zoom-out.

If users have no touchpad, they can use the key combination.
So we should adopt the same interactions as on any website.

[tinchodias]

hi! AFAIK, we don't receive the low-level events from SDL2, I hope in the future.
We should check this: https://github.com/libsdl-org/SDL_gesture

[akevalion]

moved to pharo-graphics/Roassal