When the user runs nmtui and selects an operation (edit, connect or
set-hostname) from the initial menu, the expectation is that once the
operation terminates the initial menu is shown again, so that the user
can perform multiple operations (like creating a connection and
activating it) without quitting.
https://bugzilla.gnome.org/show_bug.cgi?id=763836
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/.
