- Replace ImageField with ForeignKey reference to Image
- Update `program/show.json` fixture
- Update serializer to refer to Image and allow null

Since this may lead to errors while initialazing the container.

Closes: #163

Closes #142

- replace cc0: No Rights Reserved with pd: Public Domain
- prefix the Creative Commons License names with `cc-`
- add gfdl: GNU Free Documentation License

- updated the fixture
- updated the serializer
- updated some views