Show the path for forbidden dir in child folder

[Xpirix]

This is a proposed fix for #312

If the forbidden dir is in the root folder:

If the forbidden dir is inside a child folder:

[lnicola]

LGTM. I'd rephrase the message perhaps ("For security reasons, the ZIP file cannot contain a %s directory.", "However, there is one present at the root of the archive.") but it's clear enough already.

[Xpirix]

Thanks for the review. I think your suggestion is more precise, I've made the change.