Default table references column: 'id'

90% of my references are ```references: { table: 'some_table', column: 'id' }``` where ```id``` is the column 90% of the time. Maybe we can set some options on init:

```javascript
dirac.init({
  database: 'something'
, defaultColumnReference: 'something_other_than_id'
});
```

And we'll just make defaultColumnReference: 'id' as a default.