Archiver --dates and --stations options cannot be last. about vesper

[HaroldMills]

This issue is now fixed. I added an --end option that does nothing but terminate the list of items that follows a --dates, --stations, or --excluded-stations option. This may or may not turn out to be satisfactory. It doesn't solve the problem of leaving people who aren't aware of this potential pitfall wondering why a script doesn't work when they specify one of the --dates, --stations, or --excluded-stations options last. It would still be good to try to detect this and present an error message that explains what the problem is and how to fix it.