Expose setAllowUniversalAccessFromFileURLs in Android WebView

Summary:
This pull request exposes the `setAllowUniversalAccessFromFileURLs` method of Android WebViewSettings as a property. The reason for this is when loading pages with a `file://` baseUrl it's sometimes desirable to allow loading other assets from a file base url. (For example loading an image into a canvas). More information on its use and purpose can be found [in the android docs here](https://developer.android.com/reference/android/webkit/WebSettings.html#setAllowUniversalAccessFromFileURLs%28boolean%29)

Usage example:

``` jsx
return (
  <WebView
    source={{ html: myhtml, baseUrl: 'file://' }}
    allowUniversalAccessFromFileURLs={true}
    javaScriptEnabled={true} />
)
```
Closes https://github.com/facebook/react-native/pull/8905

Differential Revision: D4147245

Pulled By: hramos

fbshipit-source-id: 7eaa884b8c0268de52b284954a34acec0fbd4061

ReactAndroid/src/main/java/com/facebook/react/views/webview/ReactWebViewManager.java

@@ -375,6 +375,11 @@ public class ReactWebViewManager extends SimpleViewManager<WebView> {
     view.getSettings().setMediaPlaybackRequiresUserGesture(requires);
   }
 
+  @ReactProp(name = "allowUniversalAccessFromFileURLs")
+  public void setAllowUniversalAccessFromFileURLs(WebView view, boolean allow) {
+    view.getSettings().setAllowUniversalAccessFromFileURLs(allow);
+  }
+
   @ReactProp(name = "injectedJavaScript")
   public void setInjectedJavaScript(WebView view, @Nullable String injectedJavaScript) {
     ((ReactWebView) view).setInjectedJavaScript(injectedJavaScript);