Added a "version" introspection command, and beginnings of a testsuite.
Half-way implementation of the notification: Mgmt commands complete, delivery missing. Plus extensions in the helper packages to support the previous. Tweaks to the test support.
Added missing validation types, and fixed borked use of complete-enum across the board.
Reworked the handling of mail config and routes a bit.
Added support packages for mailing, and mgmt of the table of seen events.