Added write(ByteBuffer) to Streamable interface and a first draft for a NioNetworkHandler

extensions/src/main/java/ch/dissem/bitmessage/extensions/pow/ProofOfWorkRequest.java

@@ -24,6 +24,7 @@ import ch.dissem.bitmessage.utils.Encode;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.ByteBuffer;
 import java.util.Arrays;
 
 import static ch.dissem.bitmessage.utils.Decode.*;
@@ -83,6 +84,13 @@ public class ProofOfWorkRequest implements Streamable {
         Encode.varBytes(data, out);
     }
 
+    @Override
+    public void write(ByteBuffer buffer) {
+        buffer.put(initialHash);
+        Encode.varString(request.name(), buffer);
+        Encode.varBytes(data, buffer);
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;