config: Add support for formating with commented out defaults

- Changes inline comments to ; for configparser conformance
config: Add format_initial helper to populate empty configs.
utils: Add mkdir and content options to get_or_create_file

This lets callers control is parent directories are created, and set the
default content of the file.
config: Initialize config with defaults

Try and create args.config_file[-1] with the default config commented out.
We assume that the directory the config file is in exists.
config: Fix review comments.
Merge pull request #588 from adamcik/feature/config-defaults

Initialize config with commented out defaults.