Use protobuf 3 Any to avoid reflection during serialization

We currently use a home grown deserialization using cutom message properties and reflection to be able to mix different message types on the same topic.

In protobuf 3 there is a standard way to do this by using the Any type. This stores the type of the message and so allows to deserialize in a straight forward way.

See https://stackoverflow.com/questions/32613667/protobuf-3-0-any-type-pack-unpack

 Notice this change is not wire compatible.