Enumerations can have aliases, which should be documented as well.

`directivetype` is set to mimic `ClassDocumenter`. Reflect that.

`isinstance` would work on the enum members, but that is not what we want here.
`issubclass` raises a TypeError when called on objects that are not classes.

The pre check in the `ReceipeDirective.add_target_and_index() was wrong.
It checkes non-existing option "noindex", but it should check "contains"
option instead.

Keep imports alphabetically sorted and their order homogeneous across
Python source files.

The isort project has more feature and is more active than the
flake8-import-order plugin.

Most issues caught were simply import ordering from the same module.
Where imports were purposefully placed out of order, tag with
isort:skip.