Different question series types
Add group type selection to content group creation dialog
Let creators select of the following group types when creating a content group:
MIXED
QUIZ
SURVEY
FLASHCARDS
For this create DetailRadioGroupComponent
which displays radio buttons with title, description and optional icon.
Adjust content group and content editing according to group type
Hide elements which doesn't apply to group type and filter content formats.
Introduce ContentGroupResolver
for preloading content group if needed for route.
Closes #1278 (closed)