Enhancement: Redesign create and upload buttons

We have separated the "Create new file/folder" and "Upload" actions above the files list into two separate buttons,
also using the new resource type icons for more consistency.

https://github.com/owncloud/web/issues/6279
https://github.com/owncloud/web/pull/6358
https://github.com/owncloud/web/pull/6500
