Use Device configuration space for lie group operations.

[jmirabel]

Class Device has a method configuration space which return the robot configuration space (including the extra DoF). This LieGroupSpace can handle integration of a velocity, difference between configurations and could handle interpolation.

Functions integrate, difference, interpolate, etc... of include/hpp/pinocchio/configuration.hh could be implemented with the device LieGroupSpace. It would make it possible to change at runtime the interpolation method by changing the robot Lie group. Moreover, the device Lie group can be factorized (i.e. R^n x R^p becomes R^{n+p})

As a remark we should take care of later, relying on LieGroupSpace and LieGroupElement more deeply may help us to handle velocities representation correctly.