- [feature] Added reduce_columns() method

  - [feature] Added reduce_columns() method
    to select() construct, replaces columns inline
    using the util.reduce_columns utility function
    to remove equivalent columns.  reduce_columns()
    also adds "with_only_synonyms" to limit the
    reduction just to those columns which have the same
    name.  The deprecated fold_equivalents() feature is
    removed [ticket:1729].
  - [feature] Added with_labels and
    reduce_columns keyword arguments to
    Query.subquery(), to provide two alternate
    strategies for producing queries with uniquely-
    named columns.  [ticket:1729].