[src/yarp/ihead_producer.cpp] New tested version of this class.

This version:
 * contains a RingBuffer object
 * contains an UnmaskICUB object

[src/yarp/ring_buffer.cpp] Class that manages the buffers received from yarp and stores them in a circular buffer

|src/yarp/unmask_icub.cpp] Class that unmasks the events received from the iCub cameras
[CMakeLists.txt] Modification of CMakeLists.txt, so it includes the new yarp-related classes

Now CMakeLists:
 * Includes a new option indicating if we want to compile the yarp-related sources
[apps/test_ihead_producer.cpp] Application for testing the IHeadProducer class
[src/yarp/src/ihead_producer.cpp] Add of a new set_bias method

Now ihead_producer:
 * Sets the biases of the iCub cameras
[py/atis.cpp] Modification so atis.so will include the yarp-related classes

[src/yarp/src/ihead_producer.cpp] Correction of some details so the IHeadProducer class can be wrapped in Python

Now IHeadProducer:
 * Takes one more argument in the constructor (the name of the Yarp port)
 * Opens the port in the constructor

[CMakeLists.txt] Correction of some problems when compiling without Yarp

[src/yarp/src/yarp_helper.cpp] Class for managing the Yarp Network from Python

[py/recorder_ihead.py] Test application in Python
[CMakeLists.txt] Suppression of the test_ring_buffer application
[model_data/featureTracker] Add text files describing a serie of filters
adding bkp file ignoring
[components/featute_tracker] removing NaN error
[py/feature_tracker]Example py file to track crosses triangle and rectangle
[CMakeLists.txt] Correction of some errors, so it will compile when not using yarp
[src/yarp/src/yarp_helper] Correction so it will compile when not using yarp