- named_with_column becomes an attribute

- named_with_column becomes an attribute
- cleanup within compiler visit_select(), column labeling
- is_select() removed from dialects, replaced with returns_rows_text(), returns_rows_compiled()
- should_autocommit() removed from dialects, replaced with should_autocommit_text() and
should_autocommit_compiled()
- typemap and column_labels collections removed from Compiler, replaced with single "result_map" collection.
- ResultProxy uses more succinct logic in combination with result_map to target columns