Sets the child node with the specified qualified name and namespace to the given text value.
void CL_DomElement::set_child_string_ns( const CL_DomString & namespace_uri, const CL_DomString & qualified_name, const CL_DomString & value);
Detailed description:
Sets the first child node with the specified qualified name and namespace, creating it if it does not exist, to the given text value