compose: Add support for "default_target"

Currently the systemd RPM ships with default.target ->
graphical.target, which is either itself changed by Anaconda (via
parsing /etc/sysconfig/desktop, which...anyways let's stop here).

Or anaconda might set it directly to multi-user.target.

For rpm-ostree, we perform some minimal level of "preconfiguration"
per tree, so they are directly usable without an intervening
installer.

As an example for fedora-atomic/base/core, we just want
multi-user.target.  Thus, this patch provides the treefile author a
declarative mechanism to set it.
status: New builtin for system administrators to see deployments

This allows administrators to configure between deployments and easily see which deployment
they are booted into as well as indicating which is chronologically most recent.  This makes
the process more user-friendly, rather than requiring the user to remember which deployment
checksum corresponds to the most recent upgrade.
status: Rework code organization and readability

This includes several changes to format the code to follow GNU Coding Standards as per
the restof rpm-ostree.  This includes fixing indentations, adding spaces between
identifers and parentheses, replacing "goto print" with an else structure, and
reformatting print statements into complete sentences for internationalization.
status: Rework format into columns

After a discussion on what the status command should offer a
sysadmin, we decided to try a column output format similar to that
of systemctl or docker images.  This will print the timestamp,
a truncated checksum, the osname, and the refspec of each
deployment.  It also includes a --pretty option to print
the information formatted in rows with the full checksum and a
title to specify the default and the rollback target.
man: Update leading para to note "atomic" name and client/server split
man: A bit more fleshed out explanation of semantics, link to docker(1)
design/package-layering: New file

I keep explaining the vision verbally, let's write it down.
compose: Tell yum not to cache packages locally

They get deleted anyways since we blow away the tmpdir, but we expect
people to be using a local HTTP proxy.  We stopped trying to cache
packages internally as that caused conflicts with the yum lock with
concurrently executing composes.
README.md: Note that we work on the client as well
packaging: Enable hawkey and usrbinatomic by default

This will break on F20 but if that starts being a problem we can work
around it with an automatic version check or so.
Release 2014.103
compose: Add --workdir-tmpfs

This ~halves the write traffic to my SSD when doing local composes.
My laptop has 12GiB of RAM, plenty for this.
compose tree: Read in security.capability xattrs

Per http://fedoraproject.org/wiki/Features/RemoveSETUID
many programs (famously /usr/bin/ping) switched to using
"file capabilities" instead of setuid.

rpm-ostree had code to specially handle SELinux labels, but was
discarding other xattrs.  Let's just whitelist reading in
security.capability.

Closes #14
compose: Set SHADOW_USE_USRLIB

See https://bugzilla.redhat.com/show_bug.cgi?id=1098304
compose: Migrate content of /etc/{passwd,group} to /usr/lib more sanely

I had an epiphany today while working on
https://bugzilla.redhat.com/show_bug.cgi?id=1098304 - I realized that
I can just do an install, and then copy over everything except the
root entries from /etc/passwd into /usr/lib/passwd.

No need for a patched shadow-utils.  No need to modify the
/etc/nsswitch.conf before doing the install root.  It totally works.
I have no idea why I originally overcomplicated this.

The thing that sucks a bit about this code is that I have to drop to
the FILE * APIs so that I can use the glibc APIs for processing
group/shadow.

Also, the way I deduplicated the code paths for processing
passwd/group is crappy, but I think it's better than duplicating them
(as systemd-sysusers does).

The good: We don't need a two-step RPM transaction, we don't need
          a patch for shadow-utils, it's just saner
The bad: Code is not the most beautiful?  Not really bad.
The ugly: I didn't think of this in the first place and spent
          months beating my head against the wall of shadow-utils...
Namespace and share DEFINE_TRIVIAL_CLEANUP_FUNC via. rpmostree-util.h

Conflicts:
	src/rpmostree-builtin-rpm.c
Release 2014.104
wip