Merge branch 'default-display' into 'master'

add default option with no displayed div for activities and exercises

Closes #31

See merge request !34
3 jobs for master in 1 minute and 22 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #26788
test

00:00:40

 
  Deploy
passed #26789
pages

00:00:42

passed pages:deploy

00:00:01