Add telemetry message and fix prop name

Author: follesoe

protobuf_definitions/message_formats.proto

@@ -1244,5 +1244,5 @@ message SurfaceUnitBattery {
 // This message is published by the Surface Unit, and re-published by
 // the drone over the communication protocol.
 message SurfaceUnitVersionInfo {
-  string firmware_version = 1; // Surface Unit firmware version (x.y.z).
+  string version = 1; // Surface Unit firmware version (x.y.z).
 }

protobuf_definitions/telemetry.proto

@@ -287,3 +287,9 @@ message MultibeamDiscoveryTel {
 message CPUInfoTel {
   CPUInfo cpu_info = 1; // CPU information.
 }
+
+// Surface Unit telemetry message.
+message SurfaceUnitTel {
+  SurfaceUnitBatteryTel battery_info = 1; // Battery information.
+  SurfaceUnitVersionInfo version_info = 2; // Version information.
+}