Fixed issue in MousePicker with getting the closest filtered geometry
Add PhysicsHelpers class to provide static methods for common physics routines

Added a method to find the PhysicsControl on a spatial or parent.  Searches up the tree until a PhysicsControl is found.
Renamed JME_Box node in SceneObjects
Added TAP listener in SceneAppState that applies a physics impulse to any scene dynamic object selected via touch event.