Use roles instead of account names

[Fi0x]

Use role-names instead of account names when verifying, if a user is logged in or allowed to do a certain action

• This is not applicable for user-specific operations, like editing a language or recipe
• Admins should be allowed to do everything
• Roles should be stackable, for example role a can do thing a, role b can do thing b and role c can do thing a and b