Add IterableType, make TypeIsh proper class

* TypeIsh is the equivalent of JType (contains artificial constructs
  like 'String*' as well)
* The equivalent of Type is JStaticType, so update the conversions
* Add IterableType
Fix deep copy of Editor (transform children)

Editor didn’t actually perform a deep copy! Oops.
Add missing switch case to NarrowingTransformer.transformType