Only organizers should access WerWer

This includes a nice page which explains to normal users why they
aren't allowed access.
Translations for logged out page
Change links in navigation
Beginnings of profile and event pages
Merge branch 'personal_login'

This allows users to log in. Does not include a profile page or a
password reset of all users. It is only part 1 of login but it can be
released. Some changes in this branch are useful already.