Bugfix: Fix right sidebar content on small screens

We've fixed the right sidebar content on small screens because some screen sizes caused the content to flow out of the screen. Things that have been done to achieve this:

* Selection info has been removed.
* Labels of the batch actions will hide on screens <1280px if the sidebar is open.

https://github.com/owncloud/web/issues/7498
https://github.com/owncloud/web/pull/7508
