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.)
GLib/Gtk have mostly settled on the convention that two-letter
acronyms in type names remain all-caps (eg, "IO"), but longer acronyms
become initial-caps-only (eg, "Tcp").
NM was inconsistent, with most long acronyms using initial caps only
(Adsl, Cdma, Dcb, Gsm, Olpc, Vlan), but others using all caps (DHCP,
PPP, PPPOE, VPN). Fix libnm and src/ to use initial-caps only for all
three-or-more-letter-long acronyms (and update nmcli and nmtui for the
libnm changes).
Create a new clients/ subdirectory at the top level, and move cli/ and
tui/ into it, as well as nm-online.c (which was previously in test/,
which made no sense).
cli/ was split into two subdirectories, src/ and completion/. While
this does simplify things (given that the completion file and the
binary both need to be named "nmcli"), it bloats the source tree, and
we can work around it by just renaming the completion file at install
time. Then we can combine the two directories into one and just have
it all under clients/cli/.
