Better error message if the user tries to replace the root element of a document.
Better error message if the user tries to replace the root element of a document.

svn path=/trunk/eXist-1.0/; revision=1588

windauer/exist,MjAbuz/exist,jensopetersen/exist,lcahlander/exist,opax/exist,ljo/exist,olvidalo/exist,hungerburg/exist,dizzzz/exist,ljo/exist,zwobit/exist,lcahlander/exist,ambs/exist,shabanovd/exist,adamretter/exist,opax/exist,kohsah/exist,ljo/exist,eXist-db/exist,shabanovd/exist,jensopetersen/exist,ljo/exist,kohsah/exist,patczar/exist,jessealama/exist,windauer/exist,hungerburg/exist,shabanovd/exist,jessealama/exist,zwobit/exist,ambs/exist,shabanovd/exist,zwobit/exist,adamretter/exist,wolfgangmm/exist,RemiKoutcherawy/exist,adamretter/exist,jessealama/exist,wolfgangmm/exist,wolfgangmm/exist,zwobit/exist,opax/exist,olvidalo/exist,joewiz/exist,patczar/exist,windauer/exist,wshager/exist,opax/exist,kohsah/exist,eXist-db/exist,MjAbuz/exist,RemiKoutcherawy/exist,dizzzz/exist,jessealama/exist,windauer/exist,opax/exist,patczar/exist,jensopetersen/exist,patczar/exist,RemiKoutcherawy/exist,ambs/exist,ljo/exist,RemiKoutcherawy/exist,ambs/exist,RemiKoutcherawy/exist,wshager/exist,zwobit/exist,olvidalo/exist,wshager/exist,eXist-db/exist,joewiz/exist,dizzzz/exist,joewiz/exist,ambs/exist,lcahlander/exist,shabanovd/exist,ljo/exist,adamretter/exist,eXist-db/exist,windauer/exist,zwobit/exist,dizzzz/exist,kohsah/exist,hungerburg/exist,joewiz/exist,olvidalo/exist,wshager/exist,adamretter/exist,olvidalo/exist,wshager/exist,jensopetersen/exist,MjAbuz/exist,eXist-db/exist,jessealama/exist,shabanovd/exist,RemiKoutcherawy/exist,MjAbuz/exist,dizzzz/exist,wolfgangmm/exist,adamretter/exist,MjAbuz/exist,wolfgangmm/exist,joewiz/exist,wshager/exist,hungerburg/exist,patczar/exist,jessealama/exist,kohsah/exist,hungerburg/exist,lcahlander/exist,jensopetersen/exist,wolfgangmm/exist,MjAbuz/exist,jensopetersen/exist,dizzzz/exist,eXist-db/exist,windauer/exist,patczar/exist,lcahlander/exist,ambs/exist,lcahlander/exist,joewiz/exist,kohsah/exist