Spread operator

Spread a method call on all items of an iterable object.

```
let shouted = ["Golo", "is", "cool"]*: toUpperCase()
# equivalent to
["Golo", "is", "cool"]: map(|it| -> it: toUpperCase())

require(shouted oftype gololang.Tuple.class, "A spread invocation returns a tuple")
require(shouted == ["GOLO", "IS", "COOL"], "Spread invocation == aggregation of each child call")

```