Stop using navigation properties in UserStore

- Will follow up in a different PR with fixup/loading of navigation properties (they are not populated correctly today)
- Also adds some tests that load from the database (confirming that navigation properties aren't loaded today)

cc @suhasj @divega 
change to

```
protected IQueryable<TUser> LoadUserAggregate(Expression<Func<TUser, bool>> filter)
```

return base(filter).Include(u => u.Address) 

Or we can remove this and all support for child entities