A mirror child items should be also a Mirror items

[kostiakoval]

When I get a Mirror child I want to be able to use all the same methods as on original mirror
Example:

struct A {
 let a = 10
}

struct B {
 let x = [1, 2, 3]
 let a:  A()

let m = Mirror(B())
let ar = m.children[0]
ar.isArray
... etc