Optimize code and remove initialisation problems (division by zero).

Conflicts:

	src/PreviewControl/PreviewControl.cpp
	src/ZMPRefTrajectoryGeneration/OnlineStepPositionTrajectoryGeneration.cpp
	src/ZMPRefTrajectoryGeneration/OrientationsPreview.cpp
	src/ZMPRefTrajectoryGeneration/ZMPVelocityReferencedQP.cpp
Remove debug output.
Merge branch 'topic/merge-rc-3.1.4' of github.com:jrl-umi3218/jrl-walkgen into topic/merge-rc-3.1.4