Iss2 - Orientation representation in wholeBodyInterface

This branch implements the changes proposed in #2 .
I added a class Rotation and a class Frame for representing the position/orientation of the floating base of the robot with respect to the world reference frame. 
I added a module for testing these classes (wbiTest).
I updated locomotionControl accordingly.

Please check whether all tests executed by wbiTest succeed and that locomotionControl runs fine.