Communicate MDCs to the hop server

There is a request for the scimma team to send some mock packets (not necessarily conforming to the final alert schema) over the hop sever. This is mostly for diagnostic checks.

A minimum effort, easy way to achieve this is to have send the preliminary, initial, update alert notices from our MDC events. Of course there will be the disclaimer that the VOEvent schema will not be one used for the streaming alerts (this has already been pointed out in the alert service requirements document).

Depends on #388 (closed).