Fixing touch handling on resized tasks.

- Simplify touch handling just by keeping everything in screen space, 
  and just map to the curve proportionally to the arc length.  This
  makes the movement much closer to that of other lists, and prevents 
  the issue of touches at the top of the stack scrolling along the 
  curve faster than at other places (and when Recents is resized, this
  becomes more of an issue).
- Add basic functionality (disabled) for freeform task workspaces.


Change-Id: Ib3a8ce2caa1437cfc09eaa5b36aff310e29e35f5