Many app developers are discounting their apps this weekend for Labor Day weekend.  We have rounded up the best of these, take a look below. The discount for Chalkspiration has not reached the app store yet but it will be going through shortly. We’re expecting many more apps to go on sale this weekend, we’ll keep adding to this list. Aquarella/HD                         Wonderful way to render watercolour effects. Was $2.99/£1.99 – now $0.99/£0.69. Click here to download. Halftone                         Halftone 2 is now available but the developers are…