Proposal: 'Global' failure handlers for failed participants

[cer]

Currently:

• If a SagaParticipant sends back a failure message, step() onReply() must be used to update the SagaData with the error
• This can be repetitive if the application has a standardized way to handle errors

Proposed:

Define Spring @beans that implement the following interface:

interface SagaParticipantFailureHandler<T SagaData> extends Ordered   {
     void handleFailure(T, SagaData sagaData);
}

If a saga participant throws an exception, the first (sorted by Ordered) applicable - to exception and saga data - is invoked to update the SagaData prior to starting compensation.

Analogous to #86