Several nm-device-*.c files apparently originally used
nm-device-ethernet.c as a template, but missed a reference to "eth" in
class_init.

Include <linux/if_ether.h> and <linux/if_infiniband.h> from
nm-utils.h, to get ETH_ALEN and INFINIBAND_ALEN, and remove those
includes (as well as <net/ethernet.h> and <netinet/ether.h>, and
various headers that had been included to get the ARPHRD_* constants)
from other files where they're not needed now.

Remove _nm_object_ensure_inited(), etc; objects that implement
GInitable are now mandatory-to-init().

Remove constructor() implementations that sometimes return NULL; do
all the relevant checking in init() instead.

Make nm_client_new() and nm_remote_settings_new() take a GCancellable
and a GError**.

Rather than having each object type override constructed() to call
_nm_object_register_properties(), have NMObject call a virtual method
on the subclass to ask it to register them.

Move some code around in nm-client.c and nm-object.c so that all
D-Bus-related initialization happens in init_dbus(), and
non-D-Bus-related stuff stays in construct().

(This simplifies the next commit.)

Most NMObjects should not be manually created, they should only be
received from NMClient or NMRemoteSettings.

Everything currently in libnm has always been there.

This commit begins creating the new "libnm", which will replace
libnm-util and libnm-glib.

The main reason for the libnm-util/libnm-glib split is that the daemon
needs to link to libnm-util (to get NMSettings, NMConnection, etc),
but can't link to libnm-glib (because it uses many of the same type
names as the NetworkManager daemon. eg, NMDevice). So the daemon links
to only libnm-util, but basically all clients link to both.

With libnm, there will be only a single client-visible library, and
NetworkManager will internally link against a private "libnm-core"
containing the parts that used to be in libnm-util.

(The "libnm-core" parts still need to be in their own directory so
that the daemon can see those header files without also seeing the
ones in libnm/ that conflict with its own headers.)

[This commit just copies the source code from libnm-util/ to
libnm-core/, and libnm-glib/ to libnm/:

  mkdir -p libnm-core/tests/
  mkdir -p libnm/tests/
  cp libnm-util/*.[ch] libnm-util/nm-version.h.in libnm-core/
  rm -f libnm-core/nm-version.h libnm-core/nm-setting-template.[ch] libnm-core/nm-utils-enum-types.[ch]
  cp libnm-util/tests/*.[ch] libnm-core/tests/
  cp libnm-glib/*.[ch] libnm/
  rm -f libnm/libnm_glib.[ch] libnm/libnm-glib-test.c libnm/nm-glib-enum-types.[ch]
  cp libnm-glib/tests/*.[ch] libnm/tests/

]