Add support for a 'create' write operation type in addition to
the default 'index'. Using create allows specifying a unique id
for each record, and allows duplicate document detection.
Add support for checking each record returned in a bulk index
request response. Allow specifying a ruleset to send each failed
record to. Add a local variable `omes` which contains the
information in the error response, so that users can control how
to handle responses e.g. retry, or send to an error file.
Add support for response stats - count successes, duplicates, and
different types of failures.
Add testing for bulk index rejections.
