Cartesian includes a feed-forward term, in a hackyish way
Implemented the feed-forward velocity in the cartesian task in a safe way.

Now the Cartesian task accepts velocity references via the method:
setReference(desiredPose,desiredVelocity)
the old method setReference(desiredPose) sets the desired velocity to 0.
Also a getter method for the new desired velocity has been implemented
getReference(desiredPose,desiredVelocity)
Notice how the _update(x) now also resets the desired velocity for safety reasons.
TO use the feedforward term it is necessary to call a setReference
for each call to _update(x).
A possible bug has been corrected where calling setLambda caused the
desired velocity term to be miscomputed when called after setReference.
Merge branch 'devel_cartesian_has_feedforward' into DRC_eighth_sprint_week
Fixed conflicts due to the recent changes of idynutils where coman_iDyn3
has been renamed to iDyn3_model, and orientationError has been renamed to
_orientationError

Conflicts:
	src/tasks/velocity/Cartesian.cpp