Search sort

Adds support for generic querystring parameters on `client.search` (such as sorting), and added support for multiple field sorting for the search query builder. Works like this:

```javascript
// pass arbitrary querystring paramaters
db.search(COLLECTION, QUERY, {
  sort: 'value.name:asc',
  limit: 2
})

// sort by multiple fields in order
db.newSearchBuilder()
.collection('users')
.sort('name', 'desc')
.sort('age', 'asc')
.query('new york')
```