Auto-configure Bug tracker for new repos/Products

[atodorov]

When a new product is added to DB (e.g. on a new repo hook) we can configure new bug trackers to GitHub Issues for that particular repository/product. This is very straight forward.

The difficult part lies in the fact that we need a personal access token (with the repo (write)) permission so we can file issues on behalf of the user automatically. PyGithub supports API authentication with client_id/secret but according to GitHub's API docs:
https://developer.github.com/v3/#oauth2-keysecret this will only serve to increase API limits.

The app integration needs to somehow create an access token that would be used when communicating with the GitHub API.