[doc] Mention pymorse option for homebrew

While here, fix some typos
[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
[actuator] Move apply_vw_wheels in MorsePhysicsRobot class

Use this definition in both keyboard and v_omega_diff_drive  (code --)
Force the speed at (0.0, 0.0) in the construction, so the robot won't
move in an arbitrary way. Should fix #444.
[core] Add a way to retrieve gravity

While here, use it in imu instead of guessing
[ros overlays] JointTrajectoryAction is now available in control_msgs
[human builder] Use standard armature/armature pose

Instead of the 'LAAS centric' HumanPosture (which is still here is needed).

Also, the armature sensor is now automatically added. This issue has been reported
by Omar Adair Islas Ramírez on the mailing list.