Rename the included theme to Default, with 4 variants: light, dark, hc, hc-dark. This replaces Adwaita, Adwaita:dark, HighContrast and HighContrastInverse. We still make the themes available under these names, and we still set up Adwaita-dark and HighContrastInverse as the dark variants of Adwaita and HighContrast.
The unification of the theme variants under Default is not quite perfect; it would be nice to merge the assets/ and assets-hc/ subdirectories and render all assets from a single svg file.
Merging the later commits of this needs to wait until libadwaita exists and provides the Adwaita and HighContrast themes.
Still to do here:
- Include a rump icontheme, and name it 'Default'
- Provide an alternative for implementing the High-conrast a11y option. Theme switching is not great for this, now that we won't have the HighContrast theme in GTK anymore.