Updating examples

[ivanpauno]

• Moved examples from files folder to a catkin workspace style folder.
• Catkinized hello_ros example.
• Modified build_cpp and do_everything in order to build the example workspace.

TODO:

• Catkinize the other examples (I will do it in another PR).

[jubeira]

Final comments addressed; merging now! I also moved the help text to a function in the main script; just a minor detail.