Feature to contact organizer of a competition

[scorreia]

Sometimes, people want to contact the organizer (to ask questions, cancel a registration, ...)
Add a form to contact the organizer of a competition (or simply a mailto field) in the competition page.

[dmossakowski]

Now that we added email support, this should be possible but it will be limited only to the people who logged in. We cannot open it for anonymous use to avoid spam and misuse.