config.h should be included from every .c file, and it should be
included before any other include. Fix that.
(As a side effect of how I did this, this also changes us to
consistently use "config.h" rather than <config.h>. To the extent that
it matters [which is not much], quotes are more correct anyway, since
we're talking about a file in our own build tree, not a system
include.)
Split a base NMSettingIPConfig class out of NMSettingIP4Config and
NMSettingIP6Config, and update things accordingly.
Further simplifications of now-redundant IPv4-vs-IPv6 code are
possible, and should happen in the future.
Port the dbus-glib-based examples to GDBus.
Also, don't use libnm in them at all; there's not much point in
examples that use the D-Bus API directly if they're just going to fall
back to libnm for the hard stuff... (And also, this avoids the problem
that GDBus uses GVariant, while the libnm-core APIs currently still
use GHashTables.)
Also fix up some comment grammar and copyright style, and add emacs
modelines where missing.
Also rename the existing GDBus-based examples to have names ending in
"-gdbus", not "-GDBus", since there's no reason to gratuitously
capitalize here.
