Add ProgressWriterNull that doesn't print anything anywhere

src/main/java/bdv/export/ProgressWriterNull.java

+package bdv.export;
+
+import java.io.OutputStream;
+import java.io.PrintStream;
+
+public class ProgressWriterNull implements ProgressWriter
+{
+	private final PrintStream blackhole;
+
+	public ProgressWriterNull()
+	{
+		blackhole = new PrintStream( new OutputStream() {
+			@Override
+			public void write( final int b )
+			{}
+
+			@Override
+			public void write( final byte[] b )
+			{}
+
+			@Override
+			public void write( final byte[] b, final int off, final int len )
+			{}
+		} );
+	}
+
+	@Override
+	public PrintStream out()
+	{
+		return blackhole;
+	}
+
+	@Override
+	public PrintStream err()
+	{
+		return blackhole;
+	}
+
+	@Override
+	public void setProgress( final double completionRatio )
+	{}
+}