#106 Warn for missing files in nzb

[Paddington]

It happens occasionally that I have an incomplete nzb (or one that contains duplicates, or files that are from completely different dates). In principle, the naming convention is quite regular, and you normally have .rar, .r01, .r02, etc. However, with 90 files or so, it's hard to check manually if it's complete or whether .r72 is missing. A sorting option would help (maybe also sort based on size), but even better would be a warning when an incomplete nzb is found, e.g. warning, whatever.r72 is missing.