Stream facet data

For certain shapes of facet datasets, the .atomic version of the
json_query call can produce an XMPP message large enough to cause
ejabberd to fall over unceremoniously.  Switch to a streaming
CStoreEditor-based call instead to avoid this.

Ideally, this would use message bundling (aka, chunking) as well,
but the C parts of OpenSRF don't seem to support that yet.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Dan Wells <dbw2@calvin.edu>