EnsemblePlacementPolicy in 4.5 is not compatible with 4.4 clients

[eolivelli]

Is is not possible to use custom EnsemblePlacementPolicy compiled for BookKeeper 4.4 having 4.5 BookKeeper on the classpath.
It would be better to use method overloading and java8 default interface methods to make the transition to 4.5 simpler

[eolivelli]

In my specific use-case I have custom policies which extend DefaultEnsemblePlacementPolicy, so a special treatment is to be done on DefaultEnsemblePlacementPolicy to make them work

[eolivelli]

Closing as won't fix.
See the discussion on #301
In this case it is really hard to preserve compatibility, because we are not dealing only with compile time/runtime compatibility, but the problem is about the semantics of the methods

In the future we will discuss how to preserve compatibility for public APIs