Dm/traceconstraints

[danmatichuk]

support additional constraints when generating traces

• add --add-trace-constraints flag that allows for generating additional traces with constraints for the final equivalence conditions
  • Defines a trace constraint datatype in Pate.TraceConstraint that is simply: expression, comparison, constant
• add alternative what4 serializer that uses expression identifiers (based on what4 hashes/nonces) in lieu of serialized expressions
• add deserialization infrastructure for expressions-containing types, using the expression environment from the identifier-based serializer