If you launched nmtui directly into the editor for a specific
connection, it would hang with a blank screen when you quit.
Fix this by changing the way startup works a bit, and have the created
toplevel NmtNewtForm get returned all the way to nmtui.c, which can
then connect to the "quit" signal on it and quit (rather than having
the different subprograms trying to guess whether they're supposed to
quit-on-exit or not).
The main "connect" and "edit" windows set the "escape-exits" flag, but
that just closed the form without exiting the app, leaving the user
trapped. Fix this by emitting a signal when the form quits, and
catching that. (And now we don't need to watch the "clicked" signal on
the quit buttons, since they have the "exit-on-activate" flag set.)
When activating a never-before-used Wi-Fi network, we need to call
nm_client_add_and_activate_connection(), not
nm_client_activate_connection(). (We still pass a NULL connection,
since NM will attempt to auto-fill it for us, and will succeed as long
as it's not an 802.1x connection.)
We were using g_utf8_strlen() to measure strings for layout, but that
counts combining marks too, and also fails to deal with "fullwidth"
(ie, double-width) CJK characters.
Add a new utility function to do a better job of this (based on code
from vte), and use it everywhere.
