This PR removes some obsolete API.

The Flowable.dematerialize() and Observable.dematerialize() were inherently type-unsafe and have been removed. In Rx.NET, the extension methods allowed dematerialize() to be applied to Observable<Notification<T>> only, but there is no way for doing it in Java as it has no extension methods and one can't restrict a method to appear only with a certain type argument scheme.

Thereplay(Scheduler) and other overloads were carried over from the original Rx.NET API set but I can't rememeber if they had any use in the field. Most use cases capture the connectable anyway so there is no much benefit from inlining an observeOn into a connectable:

ConnectableFlowable<Integer> connectable = source.replay();
Flowable<Integr> flowable = connectable.observeOn(Schedulers.io());
// hand flowable to consumers
flowable.subscribe();
connectable.connect();