differentiate delete from close icon
use consistent icon for 'restore'/versions/history, also SVG
transparent background for lock icon
use mail icon consistent with Mail app icon
remove unused big images
remove unused loading spinners, just have one
use proper style for add icon
standardize on 32px loading spinner, decrease size in CSS where needed
use history icon in Deleted Files template as well
Optimize pictures with optipng and scour
change delete from entry forbidden sign to proper icon
Merge pull request #3757 from owncloud/icon-cleanup

Icon cleanup