refactor code

[yijiangh]

separate main function, cleaning up kuka_node

[yijiangh]

The "function" in the visualizing panel should be separated from the Qt panel objects (which only takes care of adding buttons and linking buttons to specific functions (publish associated message)). The visualization function is coupled with data and is interacting with core computation component. Thus, I think the "FrameFabWidget" should be separated from "FrameFabRvizPanel".

[yijiangh]

This issue was moved to yijiangh/choreo#1