Newt/MouseEvent: Add 'float[3] getRotation()', getWheelScale() -> getRotationScale(), refinement of commit 18cb57246372eda72c25a5cd9a69a873bdf09489

Turns out the 'wheel' semantics are not generic enough and confining rotation values
to one axis only satisfies the traditional mouse wheel.

Widen the definition of 'rotation' and delivering 3-axis if supported.

On NEWT/Android, we deliver the 2-axis for example, allowing to rotate around both
or scrolling using both directions (-> GearsES2).