Detail for specified facet

`facet_id`: "topics", "facility", "format", "genre", or "rights".

GET /api/0.2/facet/genre/
HTTP 200 OK
Allow: OPTIONS, GET
Content-Type: application/json
Vary: Accept

{
    "id": "genre",
    "model": "ddrfacet",
    "links": {
        "html": "http://ddr.densho.org/genre/",
        "json": "http://ddr.densho.org/api/0.2/facet/genre/",
        "children": "http://ddr.densho.org/api/0.2/facet/genre/children/"
    },
    "title": "Genre"
}