Adventures Models + API

[petertrotman]

We need to implement the Adventures database models and API. Should be a simple CRUD where anyone can read, any registered user can add, and both the creator user and staff users can edit and delete. Potentially we should have it so that users can carry out updates with the opportunity to rollback if the new info is bad.

Suggest the model should be similar to that described in the UX document here: https://docs.google.com/document/d/1ZYi8-XMcvkivsAJZizaNADNl2dpC3zb8yEJVsNNZFlA/edit

[whonut]

I'm going to get going on the models if that's alright. I'll probably just go from the design doc and then we can discuss things in the PR.

You might want to split the API views into a separate issue.