reproducible: show notes managed in yaml in git.debian.org/git/reproducible/notes.git. add index page for all packages with notes

reproducible: when scheduling random packages, only schedule ones which never have been attempted to be build

reproducible: use source packages names for core jobs, getting the package count down from 151 to 92 (for that job)

reproducible: send mails to the reproducible commits mailinglist. throttle to max. 3 concurrently running jobs