[Typo3-doc] Different target groups for documentation --> Terms

[Jean-Marie Schweizer]

> I agree!
> This is nearly exactly as I see it! But I think we should use the term 
> Editor instead of User. It is more disticnt, because even administrators 
> and developers are sometime users (like BE user/FE user inside Typo3)...

I would settle on Editor too since it is more clear than user.

Jean-Marie