Change: Bring UI/UX of file links sidebar in line with sharing sidebar

We adapted the UI/UX of the file links sidebar to be in line with the UI/UX of the collaborators
sidebar. The order of the two sidebars has been reversed (collaborators first, file links
second). We added info messages to support a clear understanding of the purpose of both private
and public links. Most notably the file links sidebar has no inline forms anymore.

https://github.com/owncloud/web/issues/1907
https://github.com/owncloud/web/issues/1307
https://github.com/owncloud/web/pull/2841
https://github.com/owncloud/web/pull/2917
