Bug#613724: GRUB splash image

[Osamu Aoki]

Hi,

The workaround described in https://bugs.debian.org/613724 works but
/usr/share/desktop-base/grub_background.sh is a symlink managed by
update-alternatives.

What is needed is update packaging of grub2-splashimages to create
alternatives.  Then mention way to change symlink using
update-alternatives in README.

Even better, add debconf dialogue to chose image (Maybe too much.)

Osamu