Allow the user to "group" items to reduce clutter in a busy scene

[clalancette]

In a large network, it can be hard to see all of the individual nodes, topics, services, and actions since there can be so many of them. Besides the ability to hide certain parts of the graph (which already exists), it might be nice to allow the user to "group" nodes, topics, services, and actions together into a single box. The connections would come out of the group, but they would all appear to be coming from the same place. This could significantly reduce the clutter on the screen.