Prevent bad subfolders when adding a file

[Gfy]

I saw this and have had the same issue myself before: (but I can fix mine immediately)

D:\mp3tosort2_NEW_dnb\VA-Drum_and_Bass_Headhunterz_(METH007CD)-DIRFIX-2CD-2006-TCG/000-va-drum_and_bass_headhunterz_(meth007cd)-2cd-2006-(inside)-tcg.jpg

The user should see a warning. Maybe propose an autofix. (or always autofix: pasting a windows path will keep the last directory) Also backslashes aren't allowed in the .srr file.

Related issues:

• https://bitbucket.org/Skalman/srrdb/issues/33/long-release-name-inside-uploader-dialog
• https://bitbucket.org/Skalman/srrdb/issues/40/file-from-adds-queue-starting-with-slash
• https://bitbucket.org/Skalman/srrdb/issues/48/add-file-dialog-adding-multiple-files-at