Add redirect convenience method for products and categories

[jswift]

Adding redirect targets was a bit long and annoying, so I made a simple version

Previously...

$redirect = new Redirect();
$redirect->from_path = "/old-url/$i";
$redirect->site_id   = 0;

$redirectTo = new RedirectTo();
$redirectTo->type      = RedirectTo::TYPE__PRODUCT;
$redirectTo->entity_id = 123;

$redirect->to = redirectTo;

Now...

$redirect = new Redirect();
$redirect->from_path = "/old-url/$i";
$redirect->site_id   = 0;
$redirect->toProduct(123);