The .resize `Event` has been adapted to include an _anchor_, which
provide the full necessary information for each widget where to render
on the screen with what requested size. Each Widget can then dynamically
decide how and what to render (i.e. provide placeholder text in case the
size is too small, etc.).
The App.Renderer is used for the new `Layout.render` method. Each layout
renders itself now with corresponding renderers which might only update
parts of the screen, etc.
