formatter: load templates section like a map file Since a map file has another level to select a template (spec -> mapfile -> topic), this isn't exactly the same as how a map file works. But I believe most users would expect the new behavior. A literal template is stored as an unnamed template so that it will never conflict with the templates defined in [templates] section.

test-command-template: rewrite recursion tests by using a map file A literal template will be unnamed soon, so no recursion will be practically made by using -T option.

templater: add simple interface for unnamed template (API) This provides a simpler API for callers which don't need full templating stack. Instead of storing the given template as the name specified by topic, use '' as the default template to be rendered.