Improve tutorials descriptions

[stefaniapedrazzi]

Tutorials description (http://wiki.ros.org/webots_ros/Tutorials/Sample%20Simulations) should describe in details all the steps required by to run the example.
If additional interactions other than simply starting the demo is required then it should be described in details.
For example in case of teleoperated robots, it is worth explicitly writing which window you have to select before pressing keys to move the robot.

In case of the new TIAGo example, other than writing the commands to start teleop and gmapping, it should also specify:

• run rviz and set it up
• how to activate the mapping and slam visualization
• how to set an arm target position from rviz
• how to move the robot in the environment
• etc.