main: fix loading of default target
build-sys: "link" libsystemd-id128.so with libsystemd-label

Fixed build on debian wheezy:
./.libs/libudev.so: undefined reference to `cg_create'

Appears to have no influence on the resulting binaries and
libraries. Cf. b5fafdf63f.
man: fix spacing issue in various man pages

Before: libsystemd-daemonpkg-config(1)
After: libsystemd-daemon pkg-config(1)

This fix is more complicated than it should be due to the consecutive
XML elements separated by collapsible whitespace.

Merging the lines and separating the XML elements with an en space or a
non-breaking space is the only solution that results in one, and only
one, space being inserted between them when testing. An em space results
in two spaces being inserted.
cgroup: readd proper cgroup empty tracking
cgroup: implicitly add units to GC queue when their cgroups run empty
service: correct service bus introspection for timeouts
dbus: expose cgroup properties in introspection everywhere
snapshot: snapshots are just a special kind of transient units now
systemctl: show per-unit cgroup tree correctly following the new property
core: add new "scope" unit type for making a unit of pre-existing processes

"Scope" units are very much like service units, however with the
difference that they are created from pre-existing processes, rather
than processes that systemd itself forks off. This means they are
generated programmatically via the bus API as transient units rather
than from static configuration read from disk. Also, they do not provide
execution-time parameters, as at the time systemd adds the processes to
the scope unit they already exist and the parameters cannot be applied
anymore.

The primary benefit of this new unit type is to create arbitrary cgroups
for worker-processes forked off an existing service.

This commit also adds a a new mode to "systemd-run" to run the specified
processes in a scope rather then a transient service.
core: allow setting of the description string for transient units
core: move ControlGroup and Slice properties out of the dbus "Unit" interface

Slice/ControlGroup only really makes sense for unit types which actually
have cgroups attached to them, hence move them out of the generic Unit
interface and into the specific unit type interfaces.

These fields will continue to be part of Unit though, simply because
things are a log easier that way. However, regardless how this looks
internally we should keep things clean and independent of the specific
implementation of the inside.
scope: properly implement passive validity checking of PIDs field when creating transient scopes
core: parse Slice= from the unit type specific unit file section

Since not all unit types know Slice= it belongs in the unit type
specific unit file section.
core: add support to run transient units in arbitrary slices
hwdb: remove support for (not fully implemented) conditional properties
hwdb: import data
hwdb: add --device=<device-id> and --filter=<key name glob>
keymap: remove non-existing driver string matches

There are no such strings for input devices in the kernel.
scope: make TimeoutStopUSec= settable for transient units