Fix setting "Only allow one response per user"

[jancborchardt]

Currently we have a setting "Only allow one response per user" and it’s not enabled by default. This is a bit confusing since the default being off looks like just a disabled empty checkbox, and it’s not clear why it’s empty etc.

This is why we should invert it:

• "Allow multiple responses per person" as wording
• When either "Share link" is selected or "Anonymous responses" is enabled, the checkbox will be checked and the option disabled. This makes clear that with these options, you can not prevent multiple responses.
• When switching to "Show to all users" or "Choose users", the checkbox should ideally be set by default to prevent multiple submissions on accident. It can still be unset.