Nested isolated transclude directives.
This improves/fixes the fix in d414b78717.
See the changed ng-ifunit test: The template inside ng-if should be bound to the
isolate scope of `iso` directive (resp. its child scope). Not to a child of
the root scope. This shows the issue with ng-if. It’s however problem with
other directives too.
Instead of remembering the scope, we pass around the bound parent transclusion.
56c60218d1