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.

src/capture_laser_2D.cpp

@@ -3,12 +3,7 @@
 namespace wolf {
 
 CaptureLaser2D::CaptureLaser2D(const TimeStamp& _ts, SensorBasePtr _sensor_ptr, const std::vector<float>& _ranges) :
-        CaptureBase("LASER 2D", _ts, _sensor_ptr), laser_ptr_(std::static_pointer_cast<SensorLaser2D>(sensor_ptr_.lock())), scan_(_ranges)
-{
-    //
-}
-
-CaptureLaser2D::~CaptureLaser2D()
+        CaptureBase("LASER 2D", _ts, _sensor_ptr), laser_ptr_(std::static_pointer_cast<SensorLaser2D>(getSensorPtr())), scan_(_ranges)
 {
     //
 }