Playlab go to xy

Necessary for animation in MSM (particularly quadratic motion and nonlinear acceleration). I don’t expect this
block to be used directly by students (at least not in any of our
current courses).
Tried "moveSpriteNTo" but it doesn't look right with an actor param (maybe I'm doing something wrong)
![screenshot 2014-12-05 17 57 27](https://cloud.githubusercontent.com/assets/2744615/5325712/df1fdb56-7ca8-11e4-90c0-2de25186e062.png)

alternate idea with localized string "toXY"
![screenshot 2014-12-05 18 00 40](https://cloud.githubusercontent.com/assets/2744615/5325718/0b6e217c-7ca9-11e4-807e-1249904ce2ed.png)