Better notification handling.

Better notification handling.

With this changeset you can now control which messages get notifications.
See `emchat-notify-events-type'.  Notifications still only happen if the
emchat-frame is not the current selected frame. No point in getting
notifications when it's right there in front of you.

	* emchat-log.el (emchat-notify): Rewrite using finer grained
	tuning of which events to send notifications for.

	* emchat-log.el (emchat-notify-events-type): New.

	* emchat-log.el (emchat-log): Maybe send notification after log
	has been written.  Test off of emchat-notify-flag.

Signed-off-by: Steve Youngs <steve@emchat.org>