Merge all background pictures in Backgrounds sub-directory

* Provide 3 common ratio (16x9, 16x10, 4x3) for the 2 main images.
* Avoid duplication by creating symlinks for all the screen sizes needed by
  KDE. We link to the picture with the closest ratio.
* Make all background pictures available to gnome-background-properties.
* Make the 2 main background pictures available to KDE.

debian/kali-themes-common.install

@@ -1,13 +1,12 @@
 Backgrounds/* usr/share/backgrounds/
 Color-Schemes/* usr/share/
+share/* usr/share/
 Icon-Theme/* usr/share/icons/
 Window-Theme/* usr/share/themes/
 Grub-Theme/* boot/grub/themes/
 Plymouth-Theme/* usr/share/plymouth/themes/
-Gnome-Backgrounds/* usr/share/gnome-background-properties/
 desktop-base/* usr/share/desktop-base/
+kali-logos/* usr/images/kali-logos/
 xfce/xsettings.xml usr/share/kali-themes-common/
 # Those are created by "make install"
-usr/share/desktop-base/kali-logos/
 usr/share/icons/
-usr/share/wallpapers/