Modernize gnome shell theme
Several changes to the current shell theme Including:
- Use the OSD style for popups
- Unify the OSD style
- Adapt button, entries and popup roundness to the gtk theme
- Adapt volume bars in popups and OSDs
- Adapt volume sliders in popups to the gtk theme
- osd Style for notifications anderen increased visibilty
@jimmac @bertob please test this if you have time, screenshots alone can be dull sometimes