Add "Average pageview to purchase" - do as filtered measure rather than DT

[DillonMorrison]

SELECT
( SUM(total_pagesviews_per_user) / COUNT(users) ) AS avg_pageviews_per_user
FROM (
SELECT
fullVisitorId AS users,
SUM(totals.pageviews) AS total_pagesviews_per_user
FROMbigquery-public-data.google_analytics_sample.ga_sessions_*
WHERE
_TABLE_SUFFIX BETWEEN '20170701' AND '20170731'
AND
totals.transactions >=1
GROUP BY
users )