Implement resource efficient delete all image operation

[mubeen-juks]

Hello,
The current implementation of deleteall images is throwing up resource error for large number of files. The code in deleteallimages.php is querying for all images at once and performing a delete operation. This will fail if there are large number of images and also depends on the memory limits on the server.

Request you to implement an efficient delete operation which queries and deletes the images in chunks.