Ability to flag rhetological facilities

We want to be able to flag rhetological facilities in statements.

# Design

Will be greatly inspired by [Naomi's design](https://www.figma.com/file/Ecn7dbWuRSCQuZ7S6l4wGnZ7/CaptainFact?node-id=336%3A4459):


We will also use [InformationisBeautifull's illustrations](https://informationisbeautiful.net/visualizations/rhetological-fallacies/)




# Specs

*TODO: These specs are not ready yet*

### Permissions

- Each user with reputation >= 30 should be able to add one or more flag types for each statement.

### API

API should return a new `rhetological_facilities` field in `Statement` like:

```json
{
"id": 42,
"rhetological_facilities": {
"appeal_to_nature": 4,
"hasty_generalization": 10
},
...
}
```

### Data

Rethological fallacies definitions and images will be implemented in a separate repository : https://github.com/CaptainFact/rhetological-fallacies