refactoring schema validator codebase a bit on xsd 1.1 branch. mainly have refactored XMLSchemaValidator, making it and its certain dependencies better maintainable for future.

git-svn-id: https://svn.apache.org/repos/asf/xerces/java/branches/xml-schema-1.1-dev@1517114 13f79535-47bb-0310-9956-ffa450edef68