[ENH] String-htmlization-rkris ( problems )

[denker at iam.unibe.ch]

This changet contains a methos for XMLTokenizer, which is part of
package 
Yaxo (I guess).

The change to String>>asUnHtml references HtmlEntities, which is part of
package Network-HTML.

So this can not be added in the current state. 

The change to XMLTokenizer should be submitted as a change for yaxo, and
we should think about moving asUnHtml to be part of Network-Html, no the
base system.