Add option for offset to enumerator function

[Darkmann12]

I am running into the case of already having a properly enumerated list of files, and then a batch of new files without a naming schema have been introduced. If I use enumeration on the new files then the current tool will start at 1 again and conflict with existing data. I would like to be able to add an offset so as to "continue" the enumeration pattern already in place.