Add support for composing an email in the Notmuch Emacs UI using a
mailto: URL. The mailto: URL mode is mutually exclusive with
specifying other message modifying parameters and positional
arguments.
Before this change with --auto-daemon but without --create-frame
emacs server was started but no clients stay connected to it
(in both graphical and terminal displays).
Note that this changes how --client --auto-daemon works on
graphical display; New emacs frame is now created for the
message (and message-exit-actions hook appended).
Make the default behaviour for --client the same as emacsclient
default: do not create a new frame. Add a new option --create-frame,
passing the same option to emacsclient to create a frame.
Automatically starting Emacs in daemon mode if the Emacs server is not
running is a matter of preference better not hard coded in
notmuch-emacs-mua. Add an option to control the behaviour.
Notmuch uses long options exclusively all around. The short options in
notmuch-emacs-mua are intentionally just a compatible subset of
mutt(1). Keep it this way, if only to make documenting the fact easy!
The Notmuch style --client long option remains, of course.
