Package branding-simply-linux-rv: Information

- fork for the technical preview on riscv64
  + change name (append ' RV') and versioning scheme
  + use firefox, thunderbird, xterm
  + change GTK theme to a darker one
  + add new default wallpaper stating this is
    a technical preview
  + add cpugraph widget to the pannel

- backgrounds10,xfce-settings: Move default_SL10 symlink.
- graphics: Add default.png and xdm.png in different sizes.
- backgrounds: Package Vladstudio backgrounds as separate subpackage.
- backgrounds10: Set Vladstudio "skyline" wallpaper as default.
- xfce-settings: Use symlink as default wallpaper.
- backgrounds10: Add new Vladstudio wallpapers for SL.
- xfce-settings: Use firefox on i586.
- spec: Cleanup defines of xfce4-settings helpers.
- indexhtml: Use %branding_add_conflicts macro.
- graphics,menu,indexhtml: Fix files permission mode.
- xfce-settings: Replace dm-tool with xfce4-session-logout.

- xfce-settings: Disable CSD for open/save dialogs.
- xfce-settings; Update audacious config (closes: #29014).
- indexhtml: Fix bugzilla.altllinux.org link.
- indexhtml: Fix basealt.ru links (closes: #42530).