Convert query of #findOne() to have idProperty of type ObjectID

This allows you to find by ID in your application without first having to convert your query to ObjectID on the application side:

Before:
```
userService.findOne({ _id: new ObjectID(user._id) }, function (err, entity) {})
```

After:
```
userService.findOne({ _id: user._id }, function (err, entity) {})
```