Blacklisted file orders should be removed when corresponding file has been removed

Current Situation
When a file order has been finished but the file still exists, the order is placed on the blacklist to prevent a loop (good). The order is not (or not always) removed from the blacklist, when the file has been removed later (not so good).

Desired Behavior
When a blacklisted file is removed later, JobScheduler should eventually remove the finished order from the blacklist.

Limitations
JobScheduler recognises a late file removal only under the same conditions like new files. This is, when the JobScheduler eventually needs to read new files from the watched directory.