Add defaults(), find_key(), find_last_key(), for_in(), functions(), ...

...has() and is_<type>()'s

```dict()``` objects in Python aren't ordered and don't inherit properties like Javascript. So:

```for_in = for_in_right = for_own = for_own_right```
`None` should be a valid value and count as being "set". So better to do `obj.setdefault(key, value)`.