Move User to flipper-common

Summary: Move User from reducers to flipper-common. User will now be usable by other modules.

Reviewed By: passy

Differential Revision: D37599802

fbshipit-source-id: 66412e7ed00bf27448fa2deae70f0e8e80303aba

desktop/flipper-ui-core/src/reducers/user.tsx

@@ -8,14 +8,7 @@
  */
 
 import {Actions} from './';
-
-export type User = {
-  id?: string;
-  name?: string;
-  profile_picture?: {
-    uri: string;
-  };
-};
+import {User} from 'flipper-common';
 
 export type State = User;