Wip 4199

The main difference between this pull request and the previous is that we dropped the flags on the QuorumService class.

This means letting the services decide whether or not to tick or dispatch a message by themselves, instead of letting the QuorumService know that by means of flags at time of creation.  Actually, this also makes more sense not only due to simplicity but to allow a service to make that decision on-the-fly, taking into account other factors -- which would otherwise be a bit more complicated, involving setting/unsetting flags on the QuorumService class.