Diff drive 2

This PR is on top of branch dynamic_sensor_param thus I'm pushing there.
It replaces !93 (closed) and is ready for review.

• add CaptureVelocity
• add CaptureWheelJointPosition
• add SensorDiffDrive
• add ProcessorDiffDrive
• add FeatureDiffDrive
• add ConstraintDiffDrive

Added also an example with data : $ ./test_processor_diff_drive path/to/wolf/src/test/data/diff_drive/wheel_data.dat 1.