add support for flip cards

...migrations/0023_alter_electionsfullprogrampage_content.py

main/blocks.py

main/migrations/0080_alter_mainprogrampage_program.py

main/models.py

shared/blocks/main.py

uniweb/blocks.py

...rations/0060_alter_uniwebflexiblepage_content_and_more.py

uniweb/models.py

uniweb/templates/uniweb/base.html