Parameterize Expression Helper

```javascript
{
  type: 'select'
, table: 'users'
, columns: [
    { expression: 'some_col - $1', values: [ 27 ], alias: 'foo' }
  , { expression: 'some_col - $1 - $2', values: [ 32, 33 ], alias: 'bar' }
  ]
, where: {
    id: { $gt: 100 }
  }
}

// => select some_col - $1 as "foo", some_col - $2 - $3 as "bar"
// => from "users" where "users"."id" > $4
```