RN: Nullable Image, Text, & View Props

Summary:
Changes the Flow prop types for `Image`, `Text`, and `View` to be nullable and optional.

This makes these components easier to compose.

Reviewed By: sahrens

Differential Revision: D9494285

fbshipit-source-id: c3f17147f063b31217b239a3abc085d1850f8df9

Libraries/Image/ImageProps.js

@@ -54,7 +54,7 @@ export type ImageProps = {|
   ...$Diff<ViewProps, $ReadOnly<{|style: ?ViewStyleProp|}>>,
   ...IOSImageProps,
   ...AndroidImageProps,
-  blurRadius?: number,
+  blurRadius?: ?number,
   capInsets?: ?EdgeInsetsProp,
 
   onError?: ?(event: SyntheticEvent<$ReadOnly<{||}>>) => void,
@@ -63,11 +63,11 @@ export type ImageProps = {|
   onLoadStart?: ?() => void,
   resizeMethod?: ?('auto' | 'resize' | 'scale'),
   source?: ?ImageSource,
-  style?: ImageStyleProp,
+  style?: ?ImageStyleProp,
 
   // Can be set via props or style, for now
-  height?: DimensionValue,
-  width?: DimensionValue,
+  height?: ?DimensionValue,
+  width?: ?DimensionValue,
   resizeMode?: ?('cover' | 'contain' | 'stretch' | 'repeat' | 'center'),
 
   src?: empty,