Revert "Fixed #13371"

This reverts commit 9bbd84126e80c63f0236b36c6d15eb039614f6d6.
Added abstention to values array.
Added AnswerPreviewStatisticChart.js.
Removed !important from background color.
Revised and updated AnswerPreviewBox. -complete code overhaule ,-removed
Carousel, -added list, -added statisticChart for expandingAnswers
Merge branch 'master' of git@scm.thm.de:arsnova/arsnova-mobile.git