This will allow for things like the database path to be specified
without any cheesy NOTMUCH_BASE environment variable. It also will
allow "notmuch reply" to recognize the user's email address when
constructing a reply in order to do the right thing, (that is, to use
the user's address to which mail was sent as From:, and not to reply
to the user's own addresses).
With this change, the "notmuch setup" command is now strictly for
changing the configuration of notmuch. It no longer creates the
database, but instead instructs the user to call "notmuch new" to do
that.
Now that the client sources are alone here in their own directory,
(with all the library sources down inside the lib directory), we can
break the client up into multiple files without mixing the files up.
The hope is that these smaller files will be easier to manage and
maintain.
