[AndyB] Convert attachments all 1.1

Converts attached PNG images to JPG images.

PNG images are very wasteful as they are 10 times the size of a JPG image of same size. By default all PNG images larger than 1000 KB will be converted to JPG images.

(Example of Convert attachments all page)



(Example of Convert attachments all confirm page)



(Example of Options page)



Features:
All phrases start with convertattachmentsall_ for your convenience.

How to use:
Add 'convertattachmentsall' after your forum URL.
Click the Prepare rebuild table link.
Follow instructions on the Convert attachments all confirm page.

Questions and Answers:
Q: Who can run this add-on?
A: Only admins can run this add-on.