Instead of isTerminated we now use death watch on subscribers.
! Breaking change - ActorClassification based event buses now require
and actor system. Previously no actors were involved, but now someone
has to `watch` the subscribers. The unsubscriber is an system actor,
and won't be stopped automagically if a bus stops to be used (hard to
determine what "stops being used" is)
* Replaced isTerminated checks with watching actors
* backing structure for ActorClassification swaped from
ConcurrentHashMap to immutable.Map with CAS operations on it. This is
required to avoid races and guarantee register/unregister ordering
(messages sent with proper sequence numbers) to the unsubscriber.
Performance tested it and still above 1.3million subscribe+unsubscribe
ops per second (mac i7, retina), where as the CHM version was
4 million - but that one could only work in the presence of
itTerminated - so we pay the price here for removing it.
* `ActorClassification` starts the unsubscriber instance by itself,
the unsubscriber is an system actor, and can be stopped via
`ActorClassification#shutdown`
* Will unregister from unsubscriber, when no more subscriptions for
given subscriber are left in this bus.
* Added missing "Java API: " for some types
* Updated docs to point out the automatic subscriber purging (on terminated)
c046cdff0a