Document report_error consequences

[bocekm]

Right now, from reading the documentation of actor.report_error I would have no idea why should I be using actor.report_error, for example instead of actor.log.error. Document what the consequences are when I use it - that the workflow execution may stop based on the workflow setting. Ideally link https://www.lucidchart.com/documents/edit/7935344f-9d9d-41b7-a254-b82db43fada9/0