Fix nudging so that it fires on interval, not only on mousemoves

[bhousel]

Opening an issue for a thing that I've noticed for a while.

We have a behavior called "map nudging" which will automatically pan the map if you are drawing and you get close to the edge of the map.

The nudging behavior was implemented to only pan on pointermove, but actually it should continue panning if the user is anywhere in the edge of the screen (they shouldn't need to keep jiggling the mouse to get the pans to happen)