re-add generatedata code

[willkg]

For new contributors setting up a development environment, it helps to have sample data to work with. Otherwise you don't see the site rendering things.

This was recently removed when we switched to pytest. We should re-add it.

Todo list:

1. Need to move the factories.py files out of the tests/ folder and into their respective apps. I'd keep them in factories.py test files so they don't get loaded except in development environments. Thus we don't require FactoryBoy to be installed in production environments. (If there's a better way to do this, I'm game.)
2. Re-add the test for the generate data command.
3. Re-add eadred as an INSTALLED_APPS.
4. Re-add django-eadred as a dependency.
5. Re-add sample data generation code for videos/ app.
6. Double check it all works and double-check the documentation to make sure it's still correct.

[willkg]

Instead of using factories, I'm just doing the sampledata by hand for now. Thus, there's no need to move all the factory code around.