functional enum's do not support specifing a `shape`

Using the functional API to create a `enum` does not allow for specifing a `shape`. RFC 3 does not mention the functional API at all, so I guess this is in some way intended, but it would be a useful feature for dynamically creating enum's anyways.

One can workaround this using 
```python
MyEnum = types.new_class('MyEnum', (Enum,), kwds={"shape": ...}, exec_body=lambda ns: ns[...] = ...)
``` 