Migrate to dock?

At the moment, setting the tool bar to `right` only places it as far right as the edge of the dock panel if there is one, like this:


Maybe some kind of 'dock' option, similar to 'full width' if set to 'bottom' could position it all the way to the edge (i.e as a 'dock')…

> Docks are an extension of Atom’s pane system designed to hold interface elements that you want to quickly toggle into and out of view. This is a common pattern for tool panels

See also the [blog post](http://blog.atom.io/2017/05/16/atom-1-17.html) about the new panel system.

Start by examining how the toolbar's `right` and `bottom` settings interact with Atom's dock and panel system, using the linked Atom 1.17 blog post for context. Define how a new `dock` option should behave relative to `full width`, then verify that the toolbar reaches the dock edge in the relevant positions.

Written by the indexing model from the issue text.