smoothen the trajectory of the zmpmb in the dynamic filter

Still some discontinuities in theta.

Modify the way the data of the ZMPVeolicityReferencedQP class are treated
continue the implementation of the dynamical filter of Kajita2003icra

Adding oder 7 polynome to be used to compute X,Y,Theta position for the feet.
Do a little cleanup of the computation of the foot position.

With initial position, velocity, acceleration.

(one useful commit...)