Set pagination for different API views

The response we get from the `approximate_directory_content_index` match endpoint is:

```
[
{
"fingerprint": "00000003852aabc97a0a4f477a153ef90df6d4a5",
"matched_fingerprint": "00000003852aabc97a0a4f477a153ef90df6d4a4",
"package": "http://private.purldb.io/api/packages/0bbdcf88-ad07-4970-9272-7d5f4c82cc7b/"
},
{
"fingerprint": "00000003852aabc97a0a4f477a153ef90df6d4a5",
"matched_fingerprint": "00000003852aabc97a0a4f477a153ef90df6d4a4",
"package": "http://private.purldb.io/api/packages/055a7bab-38c6-4a1d-bb57-777b72ea4c99/"
}
]
```

It would be nice to have this data returned in a similar fashion to Resources and Packages, where there is a count of results and the next and previous pages.
```
{
"count": 3,
"next": null,
"previous": null,
"results": [
....
}
```