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.
There's a bit more to it than that in general. See:
https://github.com/mossprescott/slamengine-1/blob/between/src/main/scala/slamdata/engine/functions.scala#L52

I tried switching them over and found it wasn't an improvement for most of the cases. But obviously for `Read` and `Constant` it might make sense.