87+88 frontend ux fixup sautner

Issue arsnova-click-v2#87 (closed):

• Put the button to the right.
• Changed english description to "Next question"
• Changed german descrption to "Nächste Frage"

Issue arsnova-click-v2#88 (closed):

• Added a + icon
• Changed the english description to "New question"
• Changed the german description to "Neue Frage"

closes: arsnova-click-v2#87 (closed) arsnova-click-v2#88 (closed)