github: able to list affiliated repositories by visibility
Created by: unknwon
Adds a visibility filter for listing affiliated repositories, namely "all", "private" and "public", supported by GitHub API v3.
This is particularly useful for reducing rate limit usage in syncing permissions IF the user has many public affiliated repositories as we only care about private ones.
Also the first attempt to use golden GitHub account ("sourcegraph-vcr") for producing VCRs.
Fixes #10184 (closed)