PLT-137: Disable upload button when max uploads reached (#5053)

* Change upload button color opacity when max reached

* Display max upload message

* Remove error when deleting preview

* Clear error message in side-bar

when user reaches max upload and error is displayed in side-bar, removing one file won't remove error message

* Scroll in preview after file upload in sidebar

webapp/components/file_preview.jsx

@@ -84,7 +84,10 @@ export default class FilePreview extends React.Component {
         });
 
         return (
-            <div className='file-preview__container'>
+            <div
+                className='file-preview__container'
+                ref='container'
+            >
                 {previews}
             </div>
         );