Add node screen should allow for specifying data path

This has been a bit of a challenge for a while now, making sure I file a bug so that it is tracked.

When you add a new node to the cluster view the UI of the existing cluster, there is no way to set (and no way to change afterwards) the data path. The user must instead set the data path via the CLI/REST API and then add the node to the cluster, or must add the node via its own setup screen (which is fairly uncommon to do).

Not having in the "add node" dialog also introduces a large possibility of human error by forgetting that they have a non-default path set.

It would be much more user friendly to allow this to be set when adding the node via the UI.