[url rewriting.xml] Documentation missing for <error-handler>

[joewiz]

As noted in a thread on exist-open http://markmail.org/message/y4jjzyspepkjbxgy, the URL rewriting documentation does not explain the use of <error-handler>.

Live site: http://exist-db.org/exist/apps/doc/urlrewrite.xml
GitHub source: https://github.com/eXist-db/documentation/blob/master/data/urlrewrite.xml

[xatapult]

IMHO the URL rewriting document must be rewritten completely. Once I've done all base editorial work on the documentation I will add an issue to request such a rewrite (which I might pickup myself...)

[duncdrum]

assigning Wolfgang so this doesn't get lost in the rewrite here #227