Add the questioner's email address to the question in the export file

Non-registered questioners will be given the entry "anonymous".

This feature implements the bonus option as defined in the AGQLS project.

added enhancement label

@lmas60 @tksl38 @dgrh99 If the account is deleted, the account holder's email address must be set to "anonymous" in all sessions.

@tksl38 @lmas60 The implementation of this feature will also address the color coding in the display of a question: Each question is stored with the system ID of the user. The question posers are numbered chronologically when entering the session. A click on the number highlights all questions of this question poser in color. The session owner receives a doctoral hat as an icon. The logged-in question poser gets an account icon.

added high priority label