Revert relations purge debugging
Fix newlines not showing up in Abstract/Extra fields
When renaming attachment files, keep file extension if not provided
Properly revert attachment renames if they fail. Closes #430
Merge pull request #429 from aurimasv/rename-attachment

When renaming attachment files, keep file extension if not provided
Merge branch '4.0' of https://github.com/zotero/zotero into dev

Merge from 4.0