DATAMONGO-847 - Allow usage of Query within an Update clause.

In case we detect Query within a value used for an Update value we map the query itself to build the expression to use. This allows to form query statements for e.g. $pull using the same API as for the query itself.

Update update = new Update().pull("list", query(where("value").in("foo", "bar")));

Original Pull Request: #172.