fix match token-level condition: immediately terminate and return empty match result when curr pos is outside sent

Allows for application of all rules on an annotated sequence
via apply_all method.

It was returning Position based off absolute position, which
was no good for operators like orth[first(M)] working in changing
sentence contexts.

This reflects the fact that positions stored in matches are
absolute positions, while Position type is used in the
language as position relative to current position in the
sentence context. So mixing the two was confusing at the very least.
This also actually fits the most recent version of spec,
which no longer mentions Position, either.

longest() and oneof() operator takes boost::shared_ptr<std::vector<boost::shared_ptr<ConjConditions> > >

So it's clear it's not about MatchRule at all.