Add pagenation metadata

[rockliffelewis]

Looking at the OGC API specification, there are some fields that pg_featureserv isnt returning around pagenation support

Notably the numberMatched count of available featured on the /collection/{collection}/{item} api and the Next link:

eg.

   {
      "href": "http://data.example.com/collections/buildings/items.json&offset=10&limit=2",
      "rel": "next",
      "type": "application/geo+json",
      "title": "next page"
    }

I think QGIS is expecting these things in the response so that the pagenation works properly