Add query default values

With this change, it is possible to specify default values for results in the query.

```js
db
.select('name')
.from('OUser')
.where({status: 'ACTIVE'})
.defaults({
  something: 123
})
.limit(1)
.one()
.then(function (user) {
  console.log(user.name, user.something);
});
```