Added support for raw tasks that do not require any result insertion.
Add interface for creating task objects to evaluator.
Add interface for tasks
Added list and set based tasks
Implement custom relation lookup task evaluator.
Implement custom relation match task evaluator.
Register relation lookup and match evaluators, and adapt Stratego library.
Fix several issues
Added debug logging
Set current task evaluator in evaluateTask.
Don't use EmptyTask, it has no results so it always fails.
Remove debug logging and add some documentation.
Merge branch 'efficient-relation-lookup'