Resolve "Introducing the new measure "Controversy""

Closes #743, #759, and #240

See merge request arsnova/frag.jetzt!771

# Conflicts:
#	src/app/components/shared/comment-list/comment-list.component.html
#	src/app/components/shared/comment-list/comment-list.filter.ts
#	src/assets/i18n/creator/de.json
#	src/assets/i18n/creator/en.json
#	src/assets/i18n/participant/de.json
#	src/assets/i18n/participant/en.json

Merge branch '754-add-questionwall-introduction-text-add-indicator-when-filtered-comment-list-does-not-contain' into 'staging'

add introduction, add no questions found when list is empty, i18n

Closes #754

See merge request arsnova/frag.jetzt!769

add animation

Closes #745

See merge request arsnova/frag.jetzt!768

Resolve "Keep the brainstorming heading as is"

Closes #747

See merge request arsnova/frag.jetzt!764

Resolve "Initial topic cloud configuration is broken"

Closes #749

See merge request arsnova/frag.jetzt!762

Resolve "Backdrop in comment answer is not working properly"

Closes #748

See merge request arsnova/frag.jetzt!760

Resolve "Participants see all cloud configuration options"

Closes #741

See merge request arsnova/frag.jetzt!758

Resolve "questionwall fix No.3"

Closes #744

See merge request arsnova/frag.jetzt!756

fix questionwall key support & focus bug

Closes #742

See merge request arsnova/frag.jetzt!754

fix focus bug

See merge request arsnova/frag.jetzt!750

Resolve "Configure the topic cloud for brainstorming"

Closes #731

See merge request arsnova/frag.jetzt!749