move recursion.py to evaluate folder
temporary interfaces subclass. let's see if we need to keep it
it should be _evaluator not evaluator
ImportPath has now also an _evaluator
memoize_default should always take a first argument
integrate memoize caches into evaluator
RecursionNode should be public
RecursionDecorator now also works with Evaluator caches
most evaluate representation classes probably receive the evaluator instance now
use filter_private_variable correctly in api
more improvements, so that almost all import tests pass again