Preview and voting page look alike

Fixes #400.

The preview now looks like the voting page except:
- the text boxes are smaller
- the voting button was replaced with a back button
- the interactive ```I can't give feedback``` button and the respective info box have been removed and the individual contributor boxes can't be collapsed
and this is important, because the width is now 69%, where as col-8 was 66.7% which is too narrow for the german texts in the vote row. col-9 would take too much space, so css is an easy way to customize it.