Option to set user info field as mandatory for questionnaire

In some scenarios it is legit to as for user information and make this information a mandatory. For those scenarios a new configuration is added to the user info part. The following options are possible: 

• Optional, can be left blank (current behaviour and new default setting)
• Mandatory, but editable by user (user can still enter Mikey Mouse)
• Mandatory, autofilled and not editable (input field is rendered read-only)

In the second case the input fields are rendered with a orange star to indicate the mandatoryness and the questionnaire can not be submitted if the fields are left blank

In the last case the orange star is not necessary as the fields are already populated and it might even be possible that the fields are empty (e.g. when a field is added that is not populated in the user properties).