Meeting.create: make duplicate from (optionally) mandatory

[Elblinator]

Context: The new setting from the Meta-Issue OpenSlides/openslides-meta#125

If the new setting is active then the action meeting.create requires values from „duplicate from“

[reiterl]

If in the client the duplicate-from field is set, the meeting.clone action will be called. The meeting clone action already has a required meeting id to clone/duplicate from.