Provide a collectAll() method for lists (WAS: Provide a 'SpreadAllDot' operator)

Currently we have list*.method() that invokes the method on all items in the list.
It would be useful to also support list**.method() that invokes the method on all items in the list and recursively for any lists within the list.

def animalLists= [["ant", "mouse", "elephant"], ["deer", "monkey"]]
assert animalLists.size() == 2
assert animalLists*.size() == [3, 2]
assert animalLists**.size() == [[3, 5, 8], [4, 6]]