XWIKI-9991: Top Active Contributors has empty values when the current user is local
- $xwiki.getUserName returns the proper name for inaccessible users
- the html macro makes sure to render the html escaped characters correctly while still protecting from XSS (see XWIKI-9688)

(cherry picked from commit 10b57386f427f5cf2821daf0005c715715d2741a)