Improve taskswitcher gesture animations

improves 2 gestures animations:

• diagonal quick switch now isn't super quick and can actually be followed with the eye now
• flick to homescreen is improved by scaling down the task preview instead of it becoming bigger again due to the y position being reduced (scale is tied to y position by default)
  • flick to homescreen still isn't perfect, ideally it would use proper movement speed tracking and deceleration, but it's an improvement over master IMO

fixes most of #368 (closed)