Introduce reliable retry pattern

[smaldini]

We can provide a RetryConsumer that delegates to the desired consumer to retry.

[jbrisbin]

Would this involve two Consumers, then? The first one that attempts some business logic and, if it throws an Exception, invokes a second Consumer that attempts to do something different? Not sure how this is more helpful than just doing a try/catch inside your Consumer.

[smaldini]

Now inside Stream API 2.0 (see reactive-streams) branch. Subsequent features requests to be opened separately.