Refactored transport component and renamed WritersModule.

The goal of the refactoring was to clean up the dependencies of
IncomingBatchConnection and OutgoingBatchConnection.

test/net/sf/briar/transport/NullConnectionEncrypter.java

@@ -1,26 +1,51 @@
 package net.sf.briar.transport;
 
+import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 
 /** A ConnectionEncrypter that performs no encryption. */
-class NullConnectionEncrypter implements ConnectionEncrypter {
+class NullConnectionEncrypter extends FilterOutputStream
+implements ConnectionEncrypter {
 
-	private final OutputStream out;
+	private long capacity;
 
 	NullConnectionEncrypter(OutputStream out) {
-		this.out = out;
+		this(out, Long.MAX_VALUE);
+	}
+
+	NullConnectionEncrypter(OutputStream out, long capacity) {
+		super(out);
+		this.capacity = capacity;
 	}
 
 	public OutputStream getOutputStream() {
-		return out;
+		return this;
 	}
 
 	public void writeMac(byte[] mac) throws IOException {
 		out.write(mac);
+		capacity -= mac.length;
 	}
 
-	public long getCapacity(long capacity) {
+	public long getCapacity() {
 		return capacity;
 	}
+
+	@Override
+	public void write(int b) throws IOException {
+		out.write(b);
+		capacity--;
+	}
+
+	@Override
+	public void write(byte[] b) throws IOException {
+		write(b, 0, b.length);
+	}
+
+	@Override
+	public void write(byte[] b, int off, int len) throws IOException {
+		out.write(b, off, len);
+		capacity -= len;
+	}
 }