First implementation of minimal Broker API

O.k. obviously serialization is implemented as an external responsibility here, i.e. there is no "CameraUpdateEvent" (or similar) which takes care of its own serialization/deserialization. Upon first glance, both options seem valid. Yet, this test suggests that there are two copies of the camera data: one in the vector and one in the Event; (de)serializeCamera copies the data from a) to b) or v.v. 

IIRC the whole point of using flatbuffers was that the data is stored in a "quasi-serial way" i.e. the camera data would be in a format that lends itself for direct sending. Yet, if I'm not mistaken, this would probably require dedicated message classes for every message we want to send, each of which takes care of its own, internal rep. But this is exactly what flatbuffers gives us, right?