Fixes #20963 - CVE-2017-7535 prevent XSS on org/loc host assign

Fixes #20986 - wrongly documented :user_id in ssh_keys#create

Fixes #20950 - Use 'distinct' in AR finders

Fixes #20956 - Don't pass class constants to AR conditions

Fixes #20954 - don't access MIME types via constants

Fixes #20951 - Replace render :text with :plain

Fixes #20959 - Remove :status option on 'head'

Fixes #20470 - Audit role filter changes

fixes #20653 - ui notifications for hosts with usergroup owner

Fixes #19047 - unify date formats

This introduces two new helpers for printing date in absolute and
relative format. Helper for absolute accepts also a parameter to choose
between long and short variant. The long one includes the year. The date
also has a title so you see the other format after hovering mouse...