Add link to model.*PointTool to corresponding view element

[arouinfar]

For #180

The Point Tools contain useful information in both the model and the view. It would be helpful to connect view.leftPointTool and view.rightPointTool to their corresponding model elements. I find myself trying to autoselect my way to the model with ctrl and come up with nothing.

This also means we should make the parent view elements phetioFeatured: true so the links show up in the Featured tree.

[pixelzoom]

Done in the above commits, with API change. See Studio tree screenshot below. @arouinfar please review, close if OK.

[arouinfar]

Thanks @pixelzoom. Can you also feature view.*PointToolNode so these links show up in the Featured tree?

[pixelzoom]

Can you also feature view.*PointToolNode so these links show up in the Featured tree?

Oh right, duh... you asked for that. Done in the above commits.

[arouinfar]

Looks great, thanks!

[arouinfar]

Rookie mistake, I reviewed with "All" selected.

I see that view.rightPointTool and view.LeftPointTool are featured, but the links aren't showing up because the target elements model.rightPointTool and model.leftPointTool aren't featured, just their children.

Sorry to send this back again @pixelzoom.

[pixelzoom]

Good catch, fixed in the above commits. Back to @arouinfar to verify.

[arouinfar]

Looks good in master, thanks @pixelzoom