public void writeRecursivelyTo(StringBuilder b, String pathPrefix) {
            String path = ( pathPrefix.equals("/") ? "" : pathPrefix ) + "/" + name;
            b.append(path);
            if (content.length > 0)
                b.append(" [content: ").append(content.length).append(" bytes]");
            b.append("\n");
            
            for (Node child : children.values())
                child.writeRecursivelyTo(b, path);
        }
Dumps the content of this and all children recursively to the given string builder.
Useful for debugging.

@param b the builder to write to
@param pathPrefix, the path to this node, never ending by "/"
zkfacade/src/main/java/com/yahoo/vespa/curator/mock/MemoryFileSystem.java