Add interval messages to the protocol manifest

[Archento]

trafficstars

Initially the interval_handlers of a protocol were meant to be put in the manifest since there is some form of validation going on during sending of a message and that should be reflected in the manifest.

[Archento]

This needs to be done together with the general Manifest overhaul as digests will change and we want to keep braking changes to a minimum.

Related PR: #374