Consider allowing variadic functions to operate on arrays

[springcomp]

For instance, this is currently possible:

search( merge({foo: 'bar'}, {baz: 'qux'}) , null ) -> {"foo": "bar", "baz": "qux"}

Consider supporting the following similar expression:

[{foo: 'bar'}, {baz: 'qux'}] | merge(@)

Where a potentially updated merge() function would also support an array coming from upstream expression evaluation.