Implement content backup logic, so you can recover by clicking abort when you made content changes in edit-dialog

Fix bug to submit multiple choice content, with more as one true answer, Remove notification when participant sends answer - mat-chip is enough information, Put checkbox's name in a new line

Shrink code, bugfix logic in creator's multiple choice content, add $event to all "button"-methods to prevent problems if it is interpreted as submit, add console.log in submit-method for testing, add reset-method to set all values to default after submit

Add 'answer sent' chip to participant's choice-content and implement logic to check for only 1 selected answer in single-choice mode