From ${CODE_DIR}/images/ to ${CODE_DIR}/output/images

bsdmainutils added (needed for x86-images)
Switch Mail to build@hochstift.freifunk.net

patches have to be stored under the patches/ path in your site-repo

SITE variable now identifies the site repository to use, i.e. "ffpb"
(current global one) or "wag" (Warburg), etc.

The old SITE variable is now SITE_ID to identify a specific commit. The
build-version script was adapted to be backward-compatible: SITE_ID is
still written as "site=" in the version file and the new SITE is written
as "site_repo=" and defaults on "ffpb" if it not present.

Previously, untested hardware models could not be built with this
script.

Otherwise setting VERBOSE=1 would have no effect on the build process on
its own.

This should mitigate issues with mapped /code not owned by UID 1000.