Cleanup return values in the API

The return values have to be better documented, uniform and accessible. For example query results currently mostly represent shape of the responses how it goes on the network; N1QL, Search and View results are differs, but in general it can be represented with the same QueryResult class and QueryRow.

Most of the management APIs also do not specify exact form of the result, in some cases it makes sense, e.g. info() calls, but could be better.

KV API still returns flags, which is part of the encoder implementation, and should not be visible for regular calls.