Added description of lengthPattern property

Xs:fixed is for validation only

Removed dfdl:hidden annotation and added hiddenGroupRef property to sequence

Improved property syntax form description

Added test pattern to assert and discriminator.

Added message property to discriminator

Changed long form of assert and discriminator to be consistent with format properties

Changed regular expression language to Java or PERL.

Xs:fixed is not used during parsing except to provide a default value.

It is a schema definition error is the empty sequence is the content of a complex type.

Added dfdl:UTF16Width to say if UTF-16 is fixed or variable width

Removed appendix A (UTF-16 is variable width encoding unless UFT16Width is fixed)

Clarified syntax of default value expression in defineVariable and newVariableInstances.

Added Conformance and Optional Features sections

Changed dfdl functions teston/off, seton/off to testbits and setbits

Clarifies schema definition errors on emptyValueDelimiterPolicy and nilValueDelimiterPolicy

Added prefixLength region to grammar.

Added 'none' to  dfdl:textNumberRoundingMode

Added testValueKind to assert and discriminator

Added 'suppressAtEndLax' and 'suppressedAtEndStrict'  to separatorPolicy