TO - /api/version/deliveryservices needs major optimization

The API endpoint /api/version/deliveryservices is very slow for a couple of reasons:

1. no prefetches on cdn, profile and type resulting n+1 queries
2. example urls are appended to each deliveryservice response. example urls should be returned when fetching a single deliveryservice. i.e. api/1.2/deliveryservices/42 not on the entire collection