Add an ActionAfterCommit to allow cleanup on source system.

The current design of Identity Broker commits updates to entities to the database at internally defined intervals. This additional feature will allow the connector to run cleanup functions on the source system after it is certain that the commit on Identity Broker has succeeded.

The change should add something like the following method to the Unify.Framework.Collections.EnumerableExtensions library:

public static IEnumerable<T> ActionAfterCommit<T>(this IEnumerable<T> source, Action actionOnLast);

Edit (Adam): Another possible pattern is another interface that connectors could optionally implement.