More whitespace

Taking over @raghunayyar’s https://github.com/owncloud/core/pull/3228 because I thought the changes were good and then I did some more. More breathing space, elements at least 44*44px (minimum size recommended by iOS human interface guidelines).

STILL NOT COMPLETELY DONE, so feel free to join in. Especially the Files action bar and multiselect bar. Let’s do it!

Please review, awesome @owncloud/designers!
And app devs, please check if the size increase of the left bar breaks your layout cc @tanghus @georgehrke @bartv2 @eMerzh