Add icons for network responses that are json, html, or text/plain

Skipping the 1x versions for now. We’ll just scale down the 2x assets on non-retina screens.

Classes/Utility/FLEXResources.h

@@ -19,4 +19,8 @@
 + (UIImage *)moveIcon;
 + (UIImage *)selectIcon;
 
++ (UIImage *)jsonIcon;
++ (UIImage *)textPlainIcon;
++ (UIImage *)htmlIcon;
+
 @end