[papercut] The "Saving item..." overlay should provide information about attached files and snapshots

[mronkko]

The small "Saving item..." overlay that appears on the bottom right corner of the web browser when importing an item should include information about attached items and snapshots.

The problem that this solves is the following: Even if I have chosen to automatically attach associated PDFs and other files when saving items, there is currently no way of knowing if the translator for a particular site supports saving files. The only way to know if an item was attached is to open Zotero and check if the new item has attachments.

Also a related issue is that a progress indicator of some sort would be useful because sometimes the attached files download slowly and appear with a delay. (This is probably a separate issue.)