Added a function to read limit current of the smart charger

See merge request !2

Darwin robot driver smart charger

See merge request !1

Chnaged the parameters of the arm kinematic chains.

Added functions to configure the IK and FK problems for the arm.
Updated the example XML files.

Added two functions to check if smart charger if detected and enabled.
Modified functions to access them with doubles (time in seconds and Amperes).

In terminal:
 -Default period of the smart charger and new period
 -Smart charger detected, not detected or detected and enabled
 -Start motion manager (if smart charger detected and enabled, it will execute the read operations)
 -Battery status: connected, disconnected or connected and charging
 -Shows average time to full and to empty in min (65535 it means -1)

Functions to access the smart charger module has been added to the driver of the Darwin robot.
Allows to enable or disable module, set and get period, get smart charger's data (average time to empty and to full
and battery status), read smart charger's control register (smart charger detected and/or enabled), write limit current.

Minor changes to some of the examples.

Changed the sign of the pelvis yaw angle.

Removed some unnecessary cout's.
Enhanced some of the examples to fully test all the features.

Solved a bug in the codification of some of the walk parameters.

Solved a bug in the euler angles representation.
Added some kinematic parameters to the header files.

Solved a bug in the headers installation. Both arm and leg kinematics headers were not installed due to an error in the CMakeLists.txt file.

Added the Denavit Hartenberg parameters XML files for both legs.
Added a new example to test the legs kinematics.

Added an example to test the head tracking feature.

Added an example of use of the joints motion interface.

Added the current step to the action interface.

Set a variable with the path to the darwin firmware.

Removed the local copy of the dynamixel interface registers and used the firmware version.