A few random things

1. Move wallpaper row into a separate widget with a template;
2. Fix compile-time warnings;
3. Disable horizontal scrolling;
4. Install wallpapers as files instead of bundling them via GResource;
5. Move src/wallpapers/ to data/ since they are just installed files now.
6. When changing wallpaper, copy it instead of converting to png.
7. Change wallpaper file path from ${datadir}wallpaper.png to ${datadir}/wallpaper.jpg. This breaks existing setups, but Tobias said it's fine :D