[finishes #70960432]: spritesOutsidePlayspace, edgeCollisions

2 new features here:

(1) spritesOutsidePlayspace (currently enabled only for grade 2+ freeplay levels): actors can now move outside the playspace. there is no automatic clamping to keep movements in-bounds. setSpritePosition has been expanded with 8 new positions so the student can intentionally place an actor just outside of the playspace (which allows them to appear to walk into the playspace).
![screen shot 2014-06-09 at 9 34 28 am](https://cloud.githubusercontent.com/assets/5429146/3219254/f58e950e-eff3-11e3-956c-88fc932723f9.png)

(2) edgeCollisions (currently enabled only for grade 2+ freeplay levels): related to the change above, but still potentially useful even without it. the student can now write code that responds to an event when an actor touches an edge of the playspace. 
![screen shot 2014-06-09 at 9 33 26 am](https://cloud.githubusercontent.com/assets/5429146/3219248/d5740128-eff3-11e3-977f-3f4675c7f093.png)