add seminar preview for staff
add preview block
remove preview from desk (manual url exists)
update preview import
bugfix
bugfix
bugfix
bugfix
bugfix
add professor list view
Merge branch 'prodev' into pro
add professor serializer
Add "private" field to Seminar
add migration, fix import preview
Merge branch 'prodev' into pro
move private field
Merge branch 'prodev' into pro
add preview to seminar description
bugfix
bugfix