Trajectories: refactor.
Trajectories: refactor.

	* share/urbi/trajectory-generator.u (pi/2): Defined for everybody.
	(tag): New for each instance, instead of a local variable.
	(isOver): Remove.
	(stop): New.
	(run): Adjust.
	Factor some computations.

urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi