CBQE-682: add big int values to docs

Change-Id: Id1a4fa18cb211256ad9972ab2de426c830889b9f
Reviewed-on: http://review.couchbase.org/23946
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>