Import from exported file

Summary:
This diff adds the feature to import the exported flipper data. It has the following features

- Dialog to select the file
- Merges the data with an existing store.

Reviewed By: danielbuechele

Differential Revision: D13901944

fbshipit-source-id: 1b9755735419732a34254bdc39d911bcb51ad8fe

src/chrome/MainSidebar.js

@@ -219,7 +219,6 @@ class MainSidebar extends PureComponent<MainSidebarProps> {
       numNotifications,
     } = this.props;
     let {clients, uninitializedClients} = this.props;
-
     clients = clients
       .filter(
         (client: Client) =>