ROS 2 support #23

Dear developers,

I have made some changes to make champ_setup_assistant work with ROS 2, for my project with quadruped robot. This includes robot_state_plugin for visualisation.
You can find the changes in my repository

• robot_state_plugin https://github.com/friackazoid/robot_state_plugin
• champ_setup_assistant https://github.com/friackazoid/champ_setup_assistant

For rviz python bindings I used the project of another contributor https://github.com/jrgnicho/ros2_support_utilities
Please let me know if you are interested in using this code in your project, I would appreciate any guidance on how to clean up and improve the code.