This hides the top-bar by default for everything
besides paint/sculpt workspaces.
- Use the top-bar mainly for active tool settings &
popovers panel options.
(transform / snap settings are an exception for this convention).
- Only show the top-bar (by default)
in paint work-spaces (sculpt / texture-paint / grease-pencil).
- Add an active-tool panel to the sidebar.
- Split 3D view tabs into (Item / Tool / View).
D4721 with minor changes.
Further work is needed for the top-bar and image-editor.
17a4decfea