Support BigQuery pipe syntax

[nene]

See: https://cloud.google.com/bigquery/docs/reference/standard-sql/pipe-syntax

In summary, the pipe syntax allows expressing the following SQL:

SELECT item, COUNT(*) AS num_items, SUM(sales) AS total_sales
FROM Produce
WHERE
  item != 'bananas'
  AND category IN ('fruit', 'nut')
GROUP BY item
ORDER BY item DESC;

as:

FROM Produce
|> WHERE
    item != 'bananas'
    AND category IN ('fruit', 'nut')
|> AGGREGATE COUNT(*) AS num_items, SUM(sales) AS total_sales
   GROUP BY item
|> ORDER BY item DESC;