In JVPP, introduce VppInvocationException type, which will be thrown in case VPP returns non-zero result (retval != 0, failure)
( see similar Honeycomb implementation - VppApiInvocationException )

It should be done with following condtions:

• Future and Callback facades will propagate it further on to the higher level
• If needed, Reply DTOs will not return retvals (DTO will return Reply only in case retval==0)
• It should be handled this way for all generated methods
• Requests will return either results or exception