expose groundlight.model.ImageQuery type

It would be nice to be able to write a method that takes a `groundlight.model.ImageQuery` object and use a type-hint like:

```
def parse_imagequery(iq:"groundlight.model.ImageQuery") -> str:
```

but the ImageQuery isn't exposed.  If you call `iq.__class__` you get `model.ImageQuery` which implies this might work, but it doesn't.
