upload linux-kernel metapackages
Update Debian packaging files to debhelper 9 and fix the
following Lintian tags:
E: linux-kernel-generic: copyright-should-refer-to-common-license-file-for-gpl
W: linux-kernel-generic: copyright-without-copyright-notice
W: linux-kernel-generic: description-synopsis-starts-with-article
W: linux-kernel-generic: breaks-without-version linux-generic
W: linux-kernel-generic: breaks-without-version linux-headers-generic
W: linux-kernel-generic: breaks-without-version linux-image-generic

The 'Breaks' line was completely removed as suggested by Debian:
"If the two packages can never be installed at the same time,
Conflicts should normally be used instead."
https://lintian.debian.org/tags/breaks-without-version.html