Unwind operation [WIP]

[kellrott]

Adding an unwind op to gripql that take an array in an element, and replicates it into a new element for every item in the array.

So
{ "name" : "bob", "scores" : [1,2,3] }
Becomes
{ "name" : "bob", "scores" : 1 }
{ "name" : "bob", "scores" : 2 }
{ "name" : "bob", "scores" : 3 }