ListTree UI improvements

[alasdaircr]

Hello there.

I find the ListTree view very un-intuitive and watching our users I see a lot of confusion in how to use it. There are some UX issues which could be improved upon:

1. The Nodes all show the > character even if there is no subtree. The > is only removed when the subtree has been fetched.
2. Clicking a node should expand it's content. It would be better if clicking the > and the title had the same action - in the tree view expand the subtree, and in the list view update the sub-resource list. This would reduce complexity.
3. It would be nice for a number to be visible showing the number of subresources underneath the node.

I think with these changes the component would be far more user friendly.