Add support for status bar

Summary:
This diff adds a status bar, which can be used to show the status messages, for example for Litho Support Form.
The logic for the status bar is as follows:

It maintains the array of the messages. At any point it shows the last pushed message. It will keep showing that message until it is being removed, once removed it will show second last message. The messages will be removed as and when its corresponding task/Promise is fulfilled.

Reviewed By: danielbuechele

Differential Revision: D17551495

fbshipit-source-id: 96b2f401599b9ee8a472607e6a2f027e63b3b807

src/App.tsx

@@ -36,6 +36,7 @@ import {State as Store} from './reducers/index';
 import {StaticView} from './reducers/connections';
 import PluginManager from './chrome/PluginManager';
 import BaseDevice from './devices/BaseDevice';
+import StatusBar from './chrome/StatusBar';
 const version = remote.app.getVersion();
 
 type OwnProps = {
@@ -122,6 +123,7 @@ export class App extends React.Component<Props> {
             <PluginContainer logger={this.props.logger} />
           )}
         </FlexRow>
+        <StatusBar />
         <ErrorBar text={this.props.error} />
       </FlexColumn>
     );