Refactor: Init settings using an array

Generalize the specification of default settings
to be prepared every time at server startup.
Move new settings out of the init route

Initialize settings on every server startup, rather
than only on the init route. This makes it easier to
upgrade.
Add settings for SMTP (email)
Admin: Allow changing of 'secret' settings

... but don't show them.
Add 'nodemailer' dependency
Introduce notifications

We can now send notifications via email.

This is a rough implementation of that,
a starting point, if you will.
Backlog: Only show notify icon on new stories

Turn the notification button into an icon,
and only show it on stories that have been
assigned but not confirmed.
Note when a story owner has been notified

Update the UI when a notification has been
sent. Also prevent a story owner from being notified
more than once via email.