[AndyB] Attachment editor 2.4

Fixed rotation direction when GD is enabled.

Fixed issue with image optimization and add border.

Now also properly works in direct messages.

Compatible XF 2.x versions: 2.3

Remove no longer used code in a template.

• Improved thumbnail image resolution.

• Now shows attachment size. Can now be used to convert PNG to JPG without any other changes to the image.

Updated abstracted file system code.

• Fixed issue with int precision loss.

Fixed link in conversation template.