The only reason we add this new scheduler is that we want to replace the old DefaultScheduler (and akka.util.internal.HashedWheelTimer.java). The old has in practice not been part of the public api (even though visibility modifier and doc annotation of that is missing). Therefore I suggest to rename the old to `LegacyScheduler` (or whatever) and this new one to `DefaultScheduler`.

AkkaTimer could be named akka.util.HashedWheelTimer (private[akka] internal api).