[Issue #199] Refactorization of Turtlebot plugin for Gazebo.

[fqez]

Here there is the total refactorization of the Turtlebot plugin. The code is now more clean and well structured, thus more readable. It is structured as follows (this refactorization follows the architecture of the quadrotor2 plugin by @varhub):

• One master plugin called turtlebotplugin.cc(analogous to quadrotorplugin.cc), which initialize both control, sensors and communication classes.
• One class called turtlebotsensors.cc(analogous to quadrotorsensors.cc), which control everything related with the sensors of the robot (creation, management - update - and destruction). In this case we have:
  • Camera left
  • Camera right
  • Laser
  • Pose3D
  • RGBD sensor
• One class called turtlebotcontrol.cc (analogous to quadrotorcontrol.cc), which control everything related with the actuators of the turtlebot, in this case motors.
• There is also a class in charge of ICE communications between the robot and the JdeRobot clients, called turtlebotice.cc (analogous to quadrotorice.cc). This class have a particularity, it allows to connect all the interfaces of the robot with a single endpoint, like it already happens in quadrotor2 plugin. This feature is the motivation for this refactorization.
• Finally there is a class for each turtlebot sensor/actuators which are added to the ICE adapter in order to offer their functionality to the outside.

This PR also includes a proper modification for the gazebo turtlebot model (.sdf file) so it can load the new plugin instead the ancient ones.

It only rest to cleanup the PR and update the copyright.

[aitormf]

Well done.

delete or comment the references to the other plugins (cameras and laser) in model.sdf and it can be merged

[aitormf]

Checked. It works perfectly.

you can merge it when you want