Added: UPC-E Standard Validation.
Updated: ProductValidator now accepts UPC-E standard codes when validating.
Created: UpcEExpander to expand 6, 7 and 8 digit UPC-E codes into UPC-A 12 digit codes.
Created: UpcESupressor to revert a 12 digit UPC-A code to a 6, 7 or 8 digit UPC-E Code
Added: Tests for UpcEExtender and Suppressor