Mailbox race condition fix 375
Merge pull request #449 from HCanber/dev

Fix compile error in BusLogging
Merge pull request #446 from rogeralsing/mailbox-rc-fix-375

Mailbox race condition fix 375
Fixed issue #447 - where NLog loggers wouldn't be created based on the LogClass.
Move Stash.cs to Stash\Stash.cs
Move types in Stash.cs to separate files
Move stash.cs to Internal
Move BoundedStashImpl & UnboundedStashImpl to internal namespace
Move BoundedStashImpl & UnboundedStashImpl to Internal folder
Simplify AbstractStash. Add IStash.ClearStash(). Remove IStashSupport

Originally AbstractStash was internal so this is really no breaking change.
IStashSupport isn't really needed. In Akka JVM the trait StashSupport is internal, and most of its code is in our AbstractStash
When unstashing, Terminated messages must be handled specially.
Let ActorCell create a Stash for IActorStash actors.

- Add Stash property to IActorStash
- ActorCell creates a new stash if actor implements IActorStash and hasn't set Stash itself
- ActorCell, after it has called actor.AroundPostStop & after AroundPreRestart it unstashes all messages. If the user wants another behavior the stash should be cleared in PostStop/PreRestart either by calling ClearStash or by calling UnstashAll.
- Marked UntypedActorWithBoundedStash & UntypedActorWithUnboundedStash as obsolete
- Breaking change: The property CurrentStash in WithUnboundedStash has been removed since IActorStash.Stash was introduced. Cannot find a way to make this non-breakable, but the impact should be low. Most likely, if anyone has used it, they inherited UntypedActorWithXXXStash and it still contains CurrentStash
Add overloads for filtering DeadLetters and add DeadLetter.ToString()

- EventFilterFactory.DeadLetter overloads allows a predicate to be specified
- As Eventfilter turns DeadLetters into Warnings, in order for these to be logged better DeadLetter.ToString() must output something useful.
- Fixed bug in how the error message was created. Needed to enumerate all filters. Remnant from when filters wasn't a collection.
Add ActorWithStashSpec
Add BoundedXYZ versions of all UnboundedXYZ

Currently, they are just copies.
Merge pull request #450 from mmisztal1980/i447

Fixed issue #447
Merge pull request #451 from HCanber/stashing-429

Fixes stashing #429
Fixes #459. ImplicitSender should not change when creating TestProbes
Make it possible to specify testprobe name when creating probes
Add ActorOf overload that uses ActorDsl syntax