Improve the data type returned by the accelerometer and Gyro

[alanhortz]

Instead of returning a anonymous data structure, it should be better to return a typed data object like a CartesianFloat as an argument to the onChange listener on accelerometer and gyroscope registers.

The CartesionFloat object along withe CorrectedCartesianFloat, Quaternion and EulerAngle are planned to be available in release 0.3.6 in src/registers.core.js