Burn should have a relationship type for when child bundles call their parents

[wixbot]

When a child bundle invokes its parent (e.g., uninstalling a patch bundle repairs the related parent bundle), there is no relation type passed to the parent. The parent knows it's being invoked as a related bundle (since display==embedded) but not why. See http://wixtoolset.org/issues/4490/ for more details.

Originally opened by wixbot