Rather than randomly including one or more of <glib.h>,
<glib-object.h>, and <gio/gio.h> everywhere (and forgetting to include
"nm-glib-compat.h" most of the time), rename nm-glib-compat.h to
nm-glib.h, include <gio/gio.h> from there, and then change all .c
files in NM to include "nm-glib.h" rather than including the glib
headers directly.
(Public headers files still have to include the real glib headers,
since nm-glib.h isn't installed...)
Also, remove glib includes from header files that are already
including a base object header file (which must itself already include
the glib headers).
Add a file containing the defines like DBUS_INTERFACE_DBUS from
dbus-shared.h, and use it from the gdbus-using files.
Also, convert a bunch of other places that were previously hardcoding
the string values to use the defines instead, and fix the ifcfg-rh
plugin to properly namespace its own D-Bus-related defines.
Port libnm-core/libnm to GDBus.
The NetworkManager daemon continues to use dbus-glib; the
previously-added connection hash/variant conversion methods are now
moved to NetworkManagerUtils (along with a few other utilities that
are now only needed by the daemon code).
