Feature required to create streams on the fly

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Adapters should implement the FeatureInterface CreateStreamIfNotExists when they provide such a functionality. It should be possible to turn the mechanism on or off.

EventStore has to check if adapter can handle on the fly generation and throw an exception if not.

EventStore should trigger the creation only when a new entity should be persisted and the store has no entity of same type in the identity map.

EventStore provide event-driven possiblity to abort the try.

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This feature is longer required. Prooph will offer a ZF2 migrations module which makes it easy to set up an ES and manage changes.