Do not import useless symbols.
Add a python script to convert seqplay files to sot-tools/seqplay format

  Three data files are generated to be read by entity Seqplay in sot-tool:
    - posture,
    - leaf ankle,
    - right ankle,
    - center of mass,
    - expected force in left foot,
    - expected force in right foot.
Add acceleromter and gyrometer as additional frames in Hrp2.
Add foot force sensors as additional frames.
Set gains to 1 at initialization.

  User should set his own gain after initialization.
Use AbstractHumanoidRobot attribute for accessing signals.