Re-factor "Toolbar buttons" Admin to use CSS

Need to re-factor toolbar buttons by utilizing CSS:

1. Merge enabled and disabled button images into single file and use css to extract requested image.
2. Delete hover version of images and use css/javascript to create hover image (overlay div with rounded border over enabled button).
3. Attach the list of all toolbar buttons that require attention.

Both changes should decrement total toolbar image count in distribution