Release v4.21.0

A screen now records where it sits in the application hierarchy, a navigation item records the hierarchy it was declared in, and the core package renders the toolbars a document authors - so a host can lay out and run the modeled application instead of a flat list of screens.

Added

• Screen.path (Screen.Path in .NET): the modules and features, outermost first, a screen was declared in. A destination's module/feature identity resolves against it and a host can group an unlisted screen by it. (part of #74)
• NavigationItem.hierarchy (NavigationItem.Hierarchy in .NET): the modules and features a navigation contribution was declared in. (part of #74)
• core:toolbar and core:toolbarItem in the core package. An Action item announces its command with its parameters resolved; Navigate and Dialog items execute their destination through the Scene navigation host (a screen in an outlet, a dialog) and are announced with cratis.scene.navigate outside one. presentation is honoured: mode is icon, text or both, and every hint is exposed as data-scene-presentation-<name>. See the application hierarchy and toolbars. (part of #74)

Changed

• extractNavigationItem reads the whole authored item - id, icon, presentation, destination and hierarchy - instead of only the label, target, order and group. (part of #74)