Switch to speed-based trackpoint acceleration
The current trackpoint acceleration uses deltas only but as described in https://who-t.blogspot.com/2018/06/observations-on-trackpoint-input-data.html deltas don't have enough dynamic range. We need to switch to a speed-based acceleration instead.
large configuration range for the [-1, 1] speed mapping
- acceptable at sensitivity 200
- acceptable at sensitivity 128
- acceptable at sensitivity 50
- Takes default sensitivity/hardware range into account
- replace the range attribute with a generic multiplier