Initialize List with Iterable

[Jesper Öqvist]

Add a new constructor for the List node which takes an Iterable as argument:

List.List(Iterable<ASTNode> iterable) {
  for (ASTNode node : iterable) {
    addChild(node);
  }
}

This feature was suggested by Jesper Mattsson.

[Niklas Fors]

See commit 1bbda37

[Görel Hedin]

Updated implementation to take a Collection instead of an Iterable. See commit 8d11f42. This is needed because ASTNodes are Iterables. And we don't want a call

new List(new A())

to add the children of A to the list. We want it to add A to the list.

[Görel Hedin]

Will remove this new constructor. Better to use addAll. See #139.

[Görel Hedin]

Should use addAll instead. See #139.