Refactor the current API view into a proper DRF view

[tdruez]

From #26 (comment)

pombredanne 9 days ago Owner
I would expect the returned payload to have some "header" data (e.g. some tool version, what was the query made, number of results returned, ... And to have the list of packages returned under the packages: element

See http://www.django-rest-framework.org/api-guide/generic-views/ and http://www.django-rest-framework.org/api-guide/viewsets/

[kartiksibal]

@pombredanne Regarding header data, you mean something similar to something that is added in ScanCode's JSON based results?

[tdruez]

@kartiksibal the header data was added thanks to the PackageViewSet in the latest commits.
The API now return proper headers count, next, previous.
No need to add more at this point until there's a need for it.

Current shape of the API data on the Packages endpoint:

{
    "count": 793,
    "next": "http://127.0.0.1:8000/api/packages/?limit=100&offset=100",
    "previous": null,
    "results": [
        {
            "name": "gcc-4.6",
            "version": "",
            "platform": "",
            "vulnerabilities": [
                {
                    "summary": "",
                    "cvss": null,
                    "references": [
                        {
                            "source": "",
                            "reference_id": "CVE-2002-2439",
                            "url": ""
                        }
                    ]
                }
            ],
            "references": []
        },
[...]