Concept for 'event processors'

[stoewer]

Although event processing via StreamAPI works fine, it would still be nice to have some kind of high level wrapper around the StreamAPI which provides the following features:

• Easy to use and intuitive API.
• Forwards all events to a provided callback with the signature func(events []byte) error of something similar.
• The processor automatically commits cursors if the callback returns without error.
• Has the ability to spawn and manage multiple instances of stream API in order to be able to listen on multiple partitions in parallel.
• Optimizes event processing to get a higher throughput. For example process the next batch while the last cursor is being committed.
• It must be possible to cancel event processing gracefully.