Add the ability to configure the Edit in Office permission

Problem Definition

Edit in Office permissions are currently set via giving a user Page Add permission. While this made sense when Confluence used the View File macro to embed Office content into a Confluence page - and thus editing the Office document was essentially the same as editing the page - it does not hold true anymore. The new File Preview experience clearly emphasizes the fact that Office documents are attachments, and it can be confusing to set Page Add permissions for operations involving attachments.

Suggested Solution

Change the permissions scheme used for Edit in Office to check against Attachment Add instead of Page Add.