WIP Assistant / TaskPlans / Sprint 3

Don't merge, WIP.

To test it out, switch to this branch and then run:

```
rake db:drop
rake db:migrate
rake sprint:003
rails server
```

Go to `http://localhost:3001`, sign in as the sole user (printed out in the sprint:003 run above.


Oh never mind, that's the global settings being validated against a global schema.
I think we need a new attribute to hold the task_plan schema, then you can just validate on `create_base_task` or something