Create a better ROS node visualizer tool

[mitsudome-r]

Autoware starts up many nodes at runtime as shown in the node diagram page in our documentation.
This causes rqt_graph to be very complex and hard to see the whole view of the architecture.

We could create a tool to enable better visualization of ROS Node connections by either update the existing tools or create a separate tool. Potential features that could be implemented include:

• support of ROS service (show the connection between client and server)
• Grouping multiple nodes by the same namespace into a single edge in a graph
  • rqt_graph can "group" multiple nodes by surrounding them by a box, but I would like to collapse them as a "virtual" node so that we could generate simple graph as in the following image.