Several operators has been implemented (and fixed), but still is many "non deterministics" parser warnings.

Conflicts:
	libwccl/parser/grammar.g

Some other refactoring too, some augmented comments etc.

This is to accomodate rules in future, and repurpose "Operator" to be a library api-level class for users of the library, for parsed functional operators.

It's a change from if x then y else z, which wasn't exactly proper anyway without parentheses.

So tools like valgrind don't get too excited that there's still reachable but not freed memory.

My relative position tests wouldn't compile in GCC where I used Position::Nowhere for comparison. Apparently according to standard TC1, section 9.4.2, paragraph 4, if you want to use integral static const in a program, you still have to define it even if there's initializer in the declaration.

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).

The Equals<T> now uses helper class EqualityComparer<T> and distinction is in the helper class specialisation.

Checks wether Position is_inside, is_outside, or equals to other Position given the SentenceContext.

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

Somewhat nicer to use and guards against static init order fiasco.

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.