Merge branch 'test-answer-to-text-answer' into 'master'

Change test-answer.ts to text-answer.ts

See merge request swtp-block-ws17/arsnova-angular-frontend!41

src/app/test-answer.ts → src/app/text-answer.ts

-export class TestAnswer {
+export class TextAnswer {
   id: string;
   revision: string;
   contendId: string;