Allow generating job ids via uuid4 by default

[guy-kdm]

This will enable easier persisted journaling where job-ids need to be unique. UUID based job ids are more reliable when persisting them, as they can be referenced without requesting the persistence store to supply a unique id or generating the unique id in ephemeral code. Allowing it by default for a queue will make it easier to ensure all queue consumers use uuid for job.id.

[manast]

It is already possible to specify any job id when creating jobs if the user do not want to use the pre-generated ids. Since we do not have any plans to change this behaviour I am closing this issue for now.