[ios] - support iphone6plus screensize which uses screenScale 3 and add
support for iPhone6 screen aswell
[ios] - add launch images for ip6 and ip6+ for enabling the new resolutions
[ios/vtb] - remove the video render scale down / clamp for all retina devices which have enought power to render unscaled
[ios] - add support for iPad Air 2 and iPad mini 3
Merge pull request #5390 from Memphiz/iphone6

[ios] - support iphone6plus screensize which uses screenScale 3