When receiving a message from someone not targeting our device,
we reply with an empty message that includes our own devices, so next
time they send a message they will include our device.
This change flattens messaging/chat package. It also removes dependency between multidevice and chat/protobuf packages.
The Publisher interface was also changed a bit to support more native types.
Version got bumped to 0.29.0-beta.3.
Andrea Maria Piana
Adam Babik