Allow plugins to write to the parsed protobuf (minimizes copies in some cases)

src/plugins/PositionPlugin.cpp

@@ -14,7 +14,7 @@ PositionPlugin::PositionPlugin()
     setIntervalFromNow(60 * 1000); // Send our initial position 60 seconds after we start (to give GPS time to setup)
 }
 
-bool PositionPlugin::handleReceivedProtobuf(const MeshPacket &mp, const Position *pptr)
+bool PositionPlugin::handleReceivedProtobuf(const MeshPacket &mp, Position *pptr)
 {
     auto p = *pptr;