Clarify use of Business Agreement GetStatus and Status messages and relation to BAParticipant interface

The BAWithXXXCompletionParticipant interfaces which define the API implemented by Web service-specific participant implementations (and also the participant stubs on the coordinator side) include methods with the following signatures:

public String status() throws SystemException;
public String unknown() throws SystemException;
public String error() throws SystemException;

These appear to relate (vaguely) to the BA protocol message pair GetStatus (request) and Status (response) which can be initiated from either the coordinator or the participant. If so then they appear to be inappropriate as part of the Web service-specific API. The application does not and, indeed, should not need to know about the state model employed by the protocol implementation. status() probably ought to be dropped and maybe also the other two. However, it may be that error and unknown are intended to be called during recovery processing or,perhaps, even normal processing (e.g. if the participant receives an InvalidState fault or a Failed message). So, this needs to be clarified first.

The message handlers for the i) GetStatus and ii) Status messages are currently implemented, respectively, i) to dispatch a Status message with the current (service or coordinator-side) participant engine state and ii) to do nothing. The current implementation does not ever dispatch a GetStatus message – it was not necessary to do so for the purpose of implementing recovery on either the coordinatro or the participant side. Since the BA spec provides no details as to when or how these messages are to be used the current implementation is, perhaps, appropriate, This needs to be clarified and, if necessary, the code modified to verify its use.