KING-360 Large Image iOS 8 Fix

Fixed some issues causing memory warnings, app termination, and operating system crashes when trying to view very large images. AFNetworking will now downscale the images if they are larger than 6 times the device's screen resolution.

Related changes also made here: https://github.com/doubleencore/de-MobileLite/pull/296
https://doubleencore.atlassian.net/browse/KING-360