While discussing I7539fdeada14a73ae4e18a125bb0e3947f08e8d1 Doug and
Harry realized that it would be much better if some of these values
could be specified in a config file, whether INI or YAML.
This adds a simple function to allow options to be specified in the
config file named "config.yml" in the --rel-notes-dir.
Change-Id: Ie25e1eb3da66cc627d93af585b0893469d6a7b2e
750bdc021b