Add write-method w/o input path/stream

[ingomohr]

Interface DocWriterspecifies write methods with always two parameters - a template and an output.

Now, if you don't want to use a template, you have to call.

writer.write(null, out);

Task

Pls add a method w/ only an out parameter, so that clients can call:

writer.write(out); // for both ``Path``and ``OutputStream``

(writability, readability)