Problems with 'save and send now'

There are three related problems in the _submit hook for the admin/user/notify page.

1. The two buttons currently do the same thing. That is, clicking 'save' also invokes the send-now part of the routine
2. For save-and-send-now, the settings are saved after, rather than before _notify_send() is invoked, so any new settings will be ignored. If this is really the intended behavior, the button should be named 'send now'.
3. After submitting the form, the user is taken to the home page.

The last one may be WAD, but I find it really, really irritating and believe the user should be left on the admin/user/notify page.

This patch fixes all three issues.