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/features/CMakeLists.txt

+INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})
+
+# Forward var to parent scope
+
+SET(HDRS_FEATURE ${HDRS_FEATURE}
+                 ${CMAKE_CURRENT_SOURCE_DIR}/feature_diff_drive.h PARENT_SCOPE)
+
+SET(SRCS_FEATURE ${SRCS_FEATURE}
+                 ${CMAKE_CURRENT_SOURCE_DIR}/feature_diff_drive.cpp PARENT_SCOPE)