Move all files installed below /usr/share in the same directory

Also move the grub theme to /usr/share/grub/themes/kali/ as installing
files in /boot/ is problematic on arm where /boot is often a vfat
partition that doesn't support hardlinks as required by dpkg.

Gbp-Dch: Full

debian/kali-themes-common.install

@@ -1,10 +1,4 @@
-Backgrounds/* usr/share/backgrounds/kali/
 share/* usr/share/
-Icon-Theme/* usr/share/icons/
-Window-Theme/* usr/share/themes/
-Grub-Theme/* boot/grub/themes/
-Plymouth-Theme/* usr/share/plymouth/themes/
-desktop-base/* usr/share/desktop-base/kali-theme/
 # Those are created by "make install"
 usr/share/icons/
 usr/share/images/