Initial message_bridge client and server

These will forward data, and track what made it across and what didn't
when configured correctly.  This should be off if nothing is requested
to be logged remotely.

It implements ttl, reconnects, and has a basic smoke test.

We still need to handle forwarding data for logging.

Change-Id: I7daebe8cef54029a5733b7f81ee6b68367c80d82
diff --git a/aos/network/message_bridge_client.fbs b/aos/network/message_bridge_client.fbs
new file mode 100644
index 0000000..58b653a
--- /dev/null
+++ b/aos/network/message_bridge_client.fbs
@@ -0,0 +1,24 @@
+include "aos/network/message_bridge_server.fbs";
+
+namespace aos.message_bridge;
+
+// Statistics from a single client connection to a server.
+table ClientConnection {
+  // The node that we are connected to.
+  node:Node;
+
+  // Health of this connection.  Connected or not?
+  state:State;
+
+  // Number of packets received on all channels.
+  received_packets:uint;
+
+  // TODO(austin): Per channel counts?
+}
+
+// Statistics for all clients.
+table ClientStatistics {
+  connections:[ClientConnection];
+}
+
+root_type ClientStatistics;