About /robot_description duplication

[mcres]

This ticket is aimed to suggest a couple aspects that I think would improve building upon, debugging and maintaining this repository:

1. The /robot_description topic should only be published by the /robot_state_publisher. This means that the move_group does not publish to it. When developing upon the repository, It can be very likely that both nodes have slightly different versions of such robot description, leading to difficult debugging sessions.
2. Instead of generating multiple times a robot description and pass it as a parameter to e.g. the move_group or the controller_manager nodes, these could get such information from the /robot_description topic.

This would avoid the duplication of the /robot_description publishing and consumption and make sure that it is unique.

[penglongxiang]

@mcres Thanks for your feedback, we will take a look at this issue later.