Reconcile unknown attachments

This app is for customers affected by CONFSERVER-55928 which causes attached files to show as 'unknown attachment'. This bug was fixed in 7.12.1 (backported to 7.4.9).

The app will:

• Attempt to reconcile the unknown attachment with the attached file when you view or edit a page.
• Allow people editing the page to click the unknown attachment placeholder, then choose a file from the Insert File dialog.
• Record some analytics events to help us understand the problem better (if you've opted in to Atlassian Analytics).

The app won't be able to reconcile unknown attachments if:

• The file is missing from the file system.
• The attachment title is missing from the storage format.
• The page had unpublished changes at the point the plugin attempted to reconcile the unknown attachment.

See https://confluence.atlassian.com/display/CONFKB/Unknown+attachment+error+in+Confluence+Server+and+Data+Center+7.12+and+earlier for more information.