First draft of Match value type with some tests. MatchVector does not yet properly implement first/last token, hence a test fails, and AnnotationMatch is pretty much a stub.

Note: one of the tests fails on purpose so everyone can see what it looks like.

RelativePosition operator, represented by "+" in WCCL (at least initially). Returns Nowhere for Nowhere, or a Position shifted by given offset to the position given (Begin and End are first translated into normal Positions).

It's the "setvar($V, blabla)" operator that sets $V to blabla and always returns True.

It is used wherever in WCCL variable is seen in read-only context, i.e. outside of operators that are setting its value like setvar.

Conditional operators realised as if..then..else expression and operator "? val ? pred" with some tests for StrSet specialization

add a VariableAccesor class in Variables and corresponding create_accesor and get_fast functions in Variables, plus tests

Add PositionRef value class, add Position:: nowhere/begin/end, add SentenceContext get_[abs|rel]_position takint Position or Positionref
Add tests for sc's get_*_position