Create a description field for page attachments

This task is about allowing users to add a comment with each file uploaded on the wiki. Unlike page comments, this would be a short text field, without possibility to format it, or answer it.

As it has been already mentioned on the forum, the database table which stores attachment info does has a comment field, XWA_COMMENT. It just seems to be unused. Hibernate would also allow this feature.

The proposal is to have a short text field available next to the upload button, to describe briefly the file that have been uploaded. Ideally this description would be linked to one version of the file, and could evolve with new uploads for a similar filename. On the history vien of the attachment, all successive descriptions could be visible.

This description field could be displayed in the livetable of attachments, with a filter to search in descriptions, see attached mockup: