Update for link template and immutable config core changes

- Link templates are paths again, and route name patterns are enforced
- config is immutable by default, $this->config() must be used in tests, or getEditable() from the config factory.
- pollAdd custom controller replaced with entity_form and defaults on the field definitions.
- Removed a strange old copy & paste error from aggregator module, created *is* a normal created field.
- this extended from draggable list builder, which extended from config list builder, that is now calling a method that does not exist on content entity storage. But we have no weight, so changed to extend from EntityListBuilder and cleaned up a bit.
- Definition of => Contains

Same, committed.