Implement accurate intersection and union behavior for and/or queries

Created by: rvantonder

We need to evaluate and vs. or queries quite differently due to the semantics. This function splits up the logic in evaluateOperator to evaluateAnd and evaluateOr.

The task for getting an accurate number of results for something like count:100 in an and-query is quite complex. Please see in line comments.

I'm still testing this manually. Putting this up for review now because I've converged on the implementation.