physics debug views fixes
- spriteArt moves debug view with camera
- using getChildByName in the *Art classes instead of a direct reference to the right IDebugView we were having issues on state transition when state 1 didn't have a physics debug view as getChildByName would return null apparently. a direct reference does the job better
- the previously mentioned fix also fixes the fact that while two state runs (and two physics engines run), both of their debug view will be updated and transformed by the camera instead of just one of them (because of getChildByName)