[wheeled_robot] Try to computer properly the wheel radius

In particular, it means that you do not want to consider the radious of
the CasterWheel if any.
It improves a lot the behaviour of pionner3dx
[builder] Fix the #421 fix :)

It breaks completely the morse wheeled robot in the pionner3dx case (two
wheels, one caster wheel). The new version works properly for 4 wheels
robots and 2 wheels robots + caster
[core] Make FixTurningSpeed robot generic for Physical Robot
[builder] Provide relevant FixTurningSpeed for various robot

These values are based on experimentations, I still do not understand
what cause the issue between the 'expected model' and the 'really
simulated model'
[testing/segway] Test with the default FixTurningSpeed
[testing] Relax constraint on two_segway test

The new value are more in sync with the standard segway test
[testing] Various "improvements" of pionner3d test

Remove print
Fix call to send_service_speed
Adjust slightly precision requested for the initial pose test