Tests for Definition.is_definition().
Test for an issue with named params in class calls (instead of functions).
Goto on named params in class calls is now working.
Change the behavior of eval_statement_element and follow_call_path. Arrays should only be looked at in the latter.
tests for goto on imports.
First imports are working with goto.
Refactoring: Make Import.get_all_import_names return NameParts.
Fix issues with the os module.

Using a try/finally assures that the recursion checkers work the right way.
Care for nested imports in goto_assignments.
Fix alias usages in goto_assignments.
get_parent_until should always have the same signature.

Fix it for ArrayMethod.get_parent_until.