Python Support

This story is to implement PyPI's json API. This story is successful when a second Pulp can sync from a repository published by this Pulp.

Since we want to use the resulting api for both upload from twine, and syncing from Pulp we should provide a 'live' endpoint for the packages without using Pulp's publication/distribution mechanism, since those objects are only used for a 'flat' publish.

We would need a new view that would dynamically generate the json and the url for each PythonPackageContent, the 'url' in the json would link to the location of the package in the Content View.

This new view would provide an endpoint like

/pypi/{repo-name}/{package-name}/json

for each package in a repository. This new view would not have to support upload requests from twine, as that will be done in #2887