Tri-declarative

~~~~~~~~~~~~~~~~~~~

* Fix bug in 0.33.0 when promoting callable to `Namespace`.

~~~~~~~~~~~~~~~~~~~

* Fix bug when promoting callable to `Namespace`.

* Fix handling of `EMPTY` marker.

~~~~~~~~~~~~~~~~~~~

* Added promoting callable namespace members to `Namespace` with `call_target` in
`setdefaults_path`.

~~~~~~~~~~~~~~~~~~~

* Improve `sort_after` to allow more combinations of `after=...` specifications.
e.g. by name of an entry also moved by spec.

* Changed name of first parameter of `setdefaults_path` to `__target__` to avoid
collitions with namespace parameters.

* Added `RefinableObject` base for reuse by classes wanting to be able to be configured
via constructor kwarg parameters in a declarative fashion. (The namespace of possible
constructor overrides are declared with `Refinable()` for values and the decorator
`refinable` for methods.

* Added first incarnation of crawling the definitions to recursively find available
parameters on objects and their aggregates.

* Added `Shortcut` abstraction to be able to find pre-defined set of overrides of
`RefinableObject` classes.

~~~~~~~~~~~~~~~~~~~

* `evaluate` and `evaluate_recursive` also works for methods as well as for functions.

~~~~~~~~~~~~~~~~~~~

* Fixed loop detection in flatten for `Namespace`s. This resulted in data
corruption.