updating UI documentation

Summary:
adding documentation for more of our UI components.

Deleted some unused components, which were not working anyways.

Reviewed By: jknoxville

Differential Revision: D12896109

fbshipit-source-id: 959c7864240883869ad67283f80a3c189b94bf00

src/ui/components/searchable/Searchable.js

@@ -390,4 +390,8 @@ const Searchable = (
     }
   };
 
+/**
+ * Higher-order-component that allows adding a searchbar on top of the wrapped
+ * component. See SearchableManagedTable for usage with a table.
+ */
 export default Searchable;