Documentation Update: Document the new schema properties...

Documentation Update: Document the new schema properties http://apache.org/xml/properties/schema/external-schemaLocation and http://apache.org/xml/properties/schema/external-noNamespaceSchemaLocation


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@173254 13f79535-47bb-0310-9956-ffa450edef68