Add NetworkManager.h, which includes all of the other NM header, and
require all external users of libnm to use that rather than the
individual headers.
(An exception is made for nm-dbus-interface.h,
nm-vpn-dbus-interface.h, and nm-version.h, which can be included
separately.)
"NetworkManager.h"'s name (and non-standard capitalization) suggest
that it's some sort of high-level super-important header, but it's
really just low-level D-Bus stuff. Rename it to "nm-dbus-interface.h"
and likewise "NetworkManagerVPN.h" to "nm-vpn-dbus-interface.h"
Most D-Bus interface name macros used "INTERFACE" in their name (eg,
NM_DBUS_INTERFACE), but a few used "IFACE" instead (eg,
NM_DBUS_IFACE_SETTINGS). Make them consistent.
Since the API has not changed at this point, this is mostly just a
matter of updating Makefiles, and changing references to the library
name in comments.
NetworkManager cannot link to libnm due to the duplicated type/symbol
names. So it links to libnm-core.la directly, which means that
NetworkManager gets a separate copy of that code from libnm.so.
Everything else links to libnm.
