Added a file manager container component.
Added a file manager container component.

The File Manager component wraps the FileList and Footer components
(as well as the draggable menubar), and contains state necessary to pass into its child components.

askwon/courier,askwon/Filet-Manager,askwon/Filet-Manager,askwon/Filet-Manager,askwon/courier,askwon/courier