Enhancement: Design polishing

We've polished the overall design, especially spacings and the spaces-views.

https://github.com/owncloud/web/pull/7684
https://github.com/owncloud/web/issues/6705
https://github.com/owncloud/web/issues/7676
https://github.com/owncloud/web/issues/7525
https://github.com/owncloud/web/issues/7693
https://github.com/owncloud/web/issues/7694
https://github.com/owncloud/web/issues/7685
https://github.com/owncloud/web/issues/7693
https://github.com/owncloud/web/issues/7773
