Iterate over subset of elements via `SqlRowIterator`

[Yaraslaut]

Extend SqllRowIterator to allow filtering of the data that we extract from the database
something like this:

  for (auto&& person: SqlRowIterator<Person>(stmt, [](auto& q) {
           return q.Where("age", 10).orWhere([](auto& q) {
               return q.Where("age", 20).Where("name", "John");
           });
       }))
...