Add support for returning parameters in case of error, this will allo…

[Oggerschummer]

Allow the calling app to e.g. identify which initial call went wrong by checking the return parameters.

Specification says that at least the error code and the description will be returned, but it does not limit the parameters to those two. This change allows to transfer user parameters (error code and description overrule user parameters) in case of an x-error callback. The same should be true to the x-cancel action (which is not adjusted here yet, but would work out similar). In case no user parameters are provided the behavior will be exactly the same as before.

20180129 Added delegate method to allow the application to react on missing required parameters e.g. show a message to the user before returning to the source application with an error.