API V2: Rules endpoint

[calumbell]

Currently there is no equivilent to the /sections endpoint point from API V1, which was used to get sundry rules that didn't fall under other endpoints.

When this feature was discussed over discord Discord, there was a consensus that the name /sections is not a great name for this endpoint, being both vague and the name of a HTML element. I propose that we use the /rules endpoint.

The work that needs to be undertaken can be broken down like this:

1 - Create model for storing Rules 2 - Create views to return rules, either entire articles or specific sections from an article 3 - Migrate enough data from API V1 to adaquetly test this new endpoint