Make it prefix not suffix so that sorting order
in alterator-pkg is natural instead of chaotic
during installation; turn some implicit "tools"
into explicit ones for consistency either.

This is a clone of tagged/server+sambaDC pkglist
with added metadata *and* an installer feature
to make things happen at install time; not sure
if regular-server-samba4 is going away any time
soon though as it's useful standalone too.

samba-DC-4.3.1-alt1 package set introduced task-samba-dc metapackage,
let's use that one while still carrying around what's missing there
and got collected here.