Added codegen to handle supertypes

This eliminates the need to fall back to reflection when an injected type has a (non platform) supertype. Previously, if a class had a supertype, we would fall back to reflection unless the supertype had an @Inject annotation. In fact, in order to not fall back to reflection, every (non-platform) ancestor would have to have an @Inject annotation.

This change is particularly relevant to classes with abstract supertypes that do not have members injection. The abstract supertype would have no @Inject annotation, and in its current state, Dagger would fall back to reflection.

Also note that the `ParentAdapters` that are generated only implement `MembersInjector`. That is, they are not Bindings since all we need them for is to do members injection in the parents. Additionally, we only create parent adapters when needed. So, if a class has some ancestors that have members injection and some that do not, adapters will only be generated for those that do.

This _is_ a change in behavior, and its only downside is that Dagger will no longer automatically detect if somebody swaps in a parent type from an upstream dependency without recompiling.