This adds a new flag, `-admin` for creating admin users, which can
access admin service commands, among which create-user to create other
users on-the-fly.
Since the person running the commands in the README will be the local
soju administrator, the user they create should be admin as well, hence
the README update.
Users can now specify multiple "listen" directives in their
configuration file. If -listen is specified on the CLI, it's added to
the list of listeners.
Listeners are now parsed as URLs. If the scheme is missing "ircs" is
assumed. URLs allow to enable/disable TLS on a per-listener basis and
will be used for Unix sockets too.
The default listening address is changed from irc+insecure://:6667 to
ircs://:6697. This avoids setting up an insecure listener opened to
everybody.
The database is now initialized automatically on first run. The schema
version is stored in SQLite's user_version special field. Migrations are
stored in an array and applied based on the schema version.
