CBLT-319:  pkg prefix:  couchbase-sync-gateway-{edition}

Change-Id: I770aef26ae0e82cd6ba9878854c323431f8044b1
Reviewed-on: http://review.couchbase.org/38623
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>