Make Initializers Order Independent

[dyoder]

Some initializers depend on others. For example, many event initializers depend on the shadow DOM having been attached. If they're specified in the wrong order, the event handlers won't fire appropriately. This is both brittle and difficult to debug. We need a way to ensure that either

1. Initializers run in the correct order
2. Initializers whose dependencies aren't met issue a warning

Option (1) would involve some kind of dependency mechanism. Option (2) is simpler and, although it doesn't entirely solve the problem, at least makes it easier to identify the problem.