Document difference between COUNT function in CBAS vs N1QL

The root objects that are stored in analytics datasets/collections are JSON objects. During ingestion from the Data Service all key-value pairs that are received via DCP that are not JSON objects (e.g. binary values, JSON arrays, integers, strings, ..) are filtered out and thus not stored in analytics collections.

We should clearly document this distinction and highlight any potential unexpected consequences (such as the COUNT functions returning different values in N1QL vs CBAS).