Fix flow errors

Summary: This diff fixes the flow errors that surfaced from flow-typing DialogManagerAndorid and deleting NativeDialogManagerAndroid. I also migrated all imports of NativeDialogManagerAndorid to import the module from `react-native-implementation.js`.

Reviewed By: fkgozali

Differential Revision: D15440162

fbshipit-source-id: 2fdfb68104bc8ffb93c0c77fe15aacadc182f62f

Libraries/NativeModules/specs/NativeDialogManagerAndroid.js

@@ -23,10 +23,10 @@ type DialogAction = string;
 type DialogButtonKey = number;
 export type DialogOptions = {|
   title?: string,
-  message?: string,
-  buttonPositive?: string,
-  buttonNegative?: string,
-  buttonNeutral?: string,
+  message?: Stringish,
+  buttonPositive?: Stringish,
+  buttonNegative?: Stringish,
+  buttonNeutral?: Stringish,
   items?: Array<string>,
   cancelable?: boolean,
 |};