Edit user registration for admins

[EleonoraPetzold]

Add edit function to all registrations in event results for event admins.

[EleonoraPetzold]

How to define who is admin? List of groups from the settings?

[aostrow]

probably the best way to define the group(s) in a config/settings

[EleonoraPetzold]

uses which have access rights to event in event results can edit all registrations. I think that is fine.