Create Github bot user for Eclipse SET

Summary

Eclipse SET requires a Github bot user to make authenticated http requests to Github.

Details

In builds for Eclipse SET we run into Github rate limits for unauthenticated requests as mentioned in #912 (closed). We want to use authenticated http requests as a workaround, as mentioned in #912 (comment 570713). To do this we require a Github bot user with credentials added to the SET JIPP instance. The Github bot does not require any special permissions as we do not use Github for hosting repositories.