Support inplace rename for index based selectors

[koperagen]

Either SingleColumn.named should be added, or col(Int) should return ColumnReference
Use case:

rawFrame.select { col(0) named "col1" and col(1) named "col2" }

[Jolanrensen]

A ColumnReference contains a name and path, more information than SingleColumn which is just a single column resolver. I don't think col(Int) can return it.
However, ColumnReference.named creates a RenamedColumnReference which is just a ColumnReference that, when resolved, renames the result. This should be very easily reproducible for SingleColumn, you'd just need to create a RenamedSingleColumn that also renames the result on resolve.