Users can now register beacon monitors on the settings page. Each
monitor gets a unique random token the remote program will use to
authenticate its reports. Name is the only user-supplied field for
now; more will be added as the monitor protocol is defined.
Also adds :gen_smtp to deps. Swoosh's SMTP adapter depends on
:mimemail which lives in that package, and production was 500'ing
when trying to send confirmation emails without it.
