DFDL defines entities beyond those in XSD. String converters that find and replace the DFDL entities syntax are needed.

For the "pattern entities" (like %WSP+; this replacement doesn't occur, but the raw and character entities it does.

These are needed to correctly implement almost all use of string literals in DFDL schemas.

Coverage note: Tests must insure these entities can be used in any DFDL string literal.