Failed Download Handling - Issue #322

This addresses Issue #322.

It is a port of @Tolstyak's failed download handling.  It works so far for me, but could probably use some testing, so I didn't add it to the UI and it's off by default.  I did add a readme that tells how to enable it.

While testing this, I found a weird issue with os.path.split for Windows where not having a trailing backslash on the directory causes the "Processing" folder to be one level up from the directory that was passed.  On Ubuntu, not having the trailing backslash performs as expected.  I fixed this in the kludge code (cuz, hey, it's kludgey) and tested it out.  With failed download handling deleting directories, it's bad to pass it the directory one level up -- so this solves that for windows users.  Should also fix another issue where Sickbeard's post-processing from SAB would process directories one level up.