* Refactor code. Move the C global function to a new SDWebImageCoderHelper class.
1. Create two method for animated image parse. Provide the way to allow animates on macOS
2. Create a new class called SDWebImageFrame to allow abstract usage for animated image
3. Fix EXIF orientation method will crash on iOS 7 because it’s a iOS 8 above API
* Change sd_imageLoopCount to retrieve GIF loop count for NSImage on macOS
* Adopt the refactor code, change our build-in coder with that coder helper method to reduce complexity
* Update the demo project on macOS to show animated WebP