Log all actions of github-to-gerrit in one place

Previously having them all separate made sense, since they were
launched as separate jobs. Since that isn't the case now, we
can have one central file for them all.

Use specific loggers and log handlers, since the default module
level interface does not let us change the format after it
has been set without resorting to hacks

Also fixed some really, really stupid errors in the code

Change-Id: Id9da02c4a06e4edbfc9a0d63bef68208a41b3e0b
Make repos.yaml be read from relative path of src

Change-Id: I66a8d9d804e654f1291b14809f24dd5d6fd13295