added terms of use checkbox which must be checked for signup
show upvote status in profile question list

* upvoted questions sorted to top of list

other:
* display user name instead of 'du'
fixed last participation update
added some logging for statisticsMgr
added global subscription

* global unsubscribe means unsubscribing from everything and removing question upvotes
* use bitwise comparison in upvotedQuestionsForParticipationValue
replaced header user status with profile link

* moved status to profile
change mail in profile, show confirmation for pw / mail change