BETWEEN, a more mature approach

This is a work in progress.

`RANGE` is now compiled to construct an array of values.

`Between` is now handled as follows in the planner phases:
1. an `ExprOp` is constructed, but not yet used (not the correct one yet; there will be some work to represent all the expressions we support as exprOps, but I believe everything is in place to do this work). This expression will eventually be used to translate portions of the expression to JS for use with `$where`.
2. a `Selector.And` instance is constructed which is actually used.
3. the pipeline phase has a case for `Between` so as not to fail, but does nothing interesting with it. Not sure what we actually need there, if anything.
If the between has an expr op, then the only case in which it will be annotated in the pipeline phase is the case that one or more arguments have an associated pipeline.

Which might be true in this case if there's an array attached to the argument of between.

So this could be solved by better decision logic of some type. The question is how can the decision logic be generalized in a way that applies to all cases?