Update indexes at query time

For performance reasons, don't update indexes on
document CRUD events. It's more efficient to
update them at query time.

This effectively reverts:
pull request #18 from cloudant/27388-indexing-up-to-date

And places updateAllIndexes() calls in query() and
uniqueValues().
Merge pull request #22 from cloudant/30105-update-indexes-at-query-time

30105 Update indexes at query time