Email notification of reservation capture

Email notification of reservation capture

When a reserved resource is captured, Evergreen does not notify the patron
that the resource is ready for pickup. (As far as I am aware this is true
of all versions of Evergreen that include bookings.) This could give rise
to situations where the patron goes to pick up the resource at the specified
time, only to find that it hasn't been captured and is currently unavailable.

This change gives you a checkbox to enable email notification when creating
the reservation, and adds a hook, reactor, and validator so that you can
create an action trigger to send the emails.

Signed-off-by: Mike Rylander <mrylander@gmail.com>