Required mkimage 0.3.0-alt1

Create another script for docker image, because it has no init system
for handling creation of tmpfiles.

Chroot can be two or one, work or image.
Package lists of work chroot cannot take into account packages that
will be installed into it after run-scripts.

The commit 99695713 used this variable
even though it didn't exist yet. A good reason to add this variable.

...if it's a systemd-based image; no real error then.

This is a fix to previous failures of
ve/vm + use/repo/main build attempts
(in fact, any non-distro/ targets).

SUBDIRS were just optimized away...

BASE_PACKAGES_REGEXP and THE_PACKAGES_REGEXP,
to be exact; the lack of handling these appears
to have been the culprit of firefox missing in
vm images which use/browser/firefox.

Drop duplicated code pulled into armh feature in haste
and another half-copy that made it into build-ve feature;
make ve.mk more explicit about what it actually does
regarding default nameservers (and switch it to level3
while at that, just for diversity they preach).

This change is done to reduce ambiguity in some cases;
the previous intention has been to ease navigation when
staying in a particular directory, now it's been changed
in favour of convenient toplevel `git grep' in fact.

Both variants have their pros and cons, I just find myself
leaning to this one by now hence the commit.  Feel free to
provide constructive criticism :)

Some path-related bitrot has also been fixed while at that.

Classic VEs don't carry any kernel since these are running
under a single OpenVZ (or potentially LXC) kernel image;
ARM Multiboot (TWRP in this particular case) allows to boot
off a chroot via kexec, and we need a kernel in it for that,
obviously.

No bootloader required inside such VE though.

This subprofile is akin to THE_* variables family: the configuration
bits and script hooks sitting there influence whatever chroot is
declared to be the user facing one in the end, whether it comes
from vm image or live subprofile.

The services feature ought to be a changeset of its own which would
be based on rootfs and become the base for ve/vm changes but I chose
to just do it atomically; some pre-existing duplicates are pruned now.

There was some extra duplication, just clean it up.

This further refines the modular build by making
metadata being a clearly separated feature rather
than having to rely on runtime tests, and also by
moving the code which cares for kernel bits of base
installation (.base list) in a feature of its own.

There's more to it but let's get the ball rolling first.

The missing part so far is passing "lang=ab_CD" to the kernel;
it's done with gfxboot and is somewhat doable without it...

"Alien" rather means "CentOS-based" than "xenophilic" here;
in case you still wonder: http://www.altlinux.org/Hasher/CentOS

As was noted by Alexey Shabalin in libosinfo context,
current ALT Linux images tend to lack ISO9660 metadata
-- which they did have back in the day of Master 2.4.

Please note that the data collection occurs this way
due to mkimage's config.mk resetting the values to be
empty; this was worked around by using another config
file, $(BUILDDIR)lib/iso.mk, and including it later
but that would require a separate target with per-target
CONFIG variable which isn't elegant at all given the need
to actually build up the metadata set.

So the variables were changed (to be more readable anyways)
and then proxied back to BOOT_*.  This might be cleaned up
some day after the inclusion order is tweaked or mkimage
defaults get set-if-unset-yet (?=).

A minimal chroot supporting extension via apt-get;
vitals if built on Sisyphus as of Jan 16, 2012:

  i586: 13M tar.xz, 58M chroot (33M w/o /usr/share/{doc,locale,man})
x86_64: 14M tar.xz, 60M chroot (35M w/o /usr/share/{doc,locale,man})

Trivial fixups (extra checks) added to two script hooks.

At least it shouldn't bail out when the anticipated file
just isn't there...

Initial openSUSE package base taming effort has shown that
relatively few things should be fixed; subst has been generalized
as -i option to sed(1) since its introduction, so let's just fix it.

Several targets were used in a duplicated way
that made no harm but no sense either.

Actually this is the proper rewrite that was looming ever since
tgz support was introduced: there are multiple archive formats
supported by mkimage, and there are multiple compression methods
available as well.

So the bullet got bitten yet again along with the "goal parser"
which should be more straightforward by now.

Thanks dkr@ and mithraen@ for the inspiration of this evening.

The features might get copy-pasted (or even copied-and-pruned)
when initialized; there's an unneccessary duplication of the
function name in the line adding it to FEATURES list, thus
prone to being forgotten and causing some havoc later on.

It was wrong in the first place but tackling this with some
double-colon rules ran into terminality issues, and further
tortures were considered unneccessary.

The current solution isn't perfect (no completely transparent
function name registration upon corresponding target being called)
but at least it is an improvement...

It is a current convention to prefer clearly phony targets
(see the wiki page) so let's follow it here too.

This is quite a large-scale change since mkimage-profiles got used to
baking distributions over the last year, and virtual environments are
quite different, so e.g. image.in/Makefile had to be split in two with
the main part of it moved into features.in/iso/lib/.

Short overview:

- features.in/Makefile: lib/ support
  (supporting VE images requires dynamic modifications
  to image.in/Makefile before starting the build;
  the most natural way to achieve that seems to use
  features mechanism along with makefile include dir)

- packaging format related part moved into features.in/pack
  (should be better prepared for diversity either)
- features.in/iso renamed to features.in/build-distro
- features.in/ve  renamed to features.in/build-ve
  + NB: these could not be merged as e.g. features.in/build
    due to completely different script hooks

- lib/image.mk renamed to lib/build.mk
- image, config, log postprocessing moved downstream
- added a sort of a topping in the form of lib/sugar.mk
- assorted style fixups (like ifeq usage)

- clean.mk: reliability fix (the problem was observed by Oleg Ivanov
  and me too but finally it did get the attention quantum)

- reviewed, updated and extended docs
  + QUICKSTART: should be[come] a step-by-step guide
    (thanks Leo-sp50 for prodiving feedback)