This adds a short note for the new iallocator mode.

Signed-off-by: Iustin Pop <iustin@google.com>

This reduces warnings from lintian when building Debian packages.

hn1 was deprecated for a while and this patch removes it altogether. The
support code in Cluster.hs is also removed.

This doc-patch adds copyright and license information to (hopefully) all
needed files.