Nested models issue

We have a situation like so:

```
model FuelLog {
model FuelLogLocation {
...props
}
}
```

This doesn't work with the reference pool (on FuelLog) because the snapshot assignment causes duplicate content (not entirely sure the mechanics, but I get the issue - the container implies some pooling or at least awareness of the model properties. I don't have an easy answer, but figured I'd put it out there.

Start by reproducing the nested FuelLog/FuelLogLocation example and examining how snapshot assignment interacts with the reference pool on FuelLog. The issue needs a clearly defined expected result before implementation; done should mean nested models no longer produce duplicate content, with the behavior verified by a regression test.

Written by the indexing model from the issue text.