Allow deferred assignment of jobName and jobExecutionId in job schedule configuration

In class org.jberet.schedule.JobScheduleConfig, fields jobName and jobExecutionId are currently set upon instance construction. When used in processing REST API calls, this requires all such fields to be present in the request payload. In some cases, information such as jobName and jobExecutionId are already included as part of request url, and therefore users should not be forced to repeat the same information in a request.

We shoudl allow them to be set later in the processing cycle, where they can be extracted from request url and update the job schedule configuration instance accordingly.