[J] Thread Preview 1.7.1

Note: if the post contain only images then it will display nothing as i had intentionally removed it, though if you want to display that you can make template change but that will display complete message of the post.

List of things left:

1. Enable/Disable option
2. Usergroup permissions
3. Add options for display format
   1. last post preview only
   2. first post preview only
   3. last unread post preview
   4. first + last post preview only
   5. last + last unread post preview
   6. first + last unread post preview
   7. All three together preview
   8.