Improve the visual appearance of the devtab toolbar
Improves the visual appearance of the Devtab Grid Toolbar by making the toolbar a linked widget with the Devtab Grid above. This prevents the odd visual look currently where the buttons in the toolbar have squared-off corners on the insides, while maintaining the UX-based separation of the 'delete-partition' button (which is destructive) from the other buttons.
Fixes #223 (closed)