Align tree lines in the widget inspector better

[goderbauer]

Currently, the widget inspector looks like this:

I believe, the parent-child relationship in the multi-child case could be made even clearer by aligning the lines that symbolize the tree a little better, see this mock:

For the single child case the line representing the tree connects the icons directly. For some reason, in the multi child case that line comes out of the down arrow instead. I think it would be clearer if in that case the line is also coming out of the icon instead (see mock above). That visualizes the tree structure better, IMO.

PS: I still love how clean this new unindented presentation style of the widget tree looks without sacrificing any of its utility.

[goderbauer]

cc @kenzieschmoll @elliette