Doxygen builder: added support of PREDEFINED tag

- Doxygen builder: (optional) override Doxygen PREDEFINED property.
- Introduce uninstall target

Follows discussion http://answers.ros.org/question/154676/how-to-introduce-the-doxygen-predefined-tag-in-rosdoc_lite/?answer=154841#post-id-154841

Fabien