publish: Make publisher more powerful and better exposed on the command line. * Make the `chef publish` command have one sub-command per publish target. * Add custom argument parsing per publisher to have strong extra arguments available per publish target. * Make publish targets a first class citizen of the `PieCrust` app class.

from piecrust.serving.server import WsgiServer


def get_app(root_dir, cache_key='prod', enable_debug_info=False):
    app = WsgiServer(root_dir,
                     cache_key=cache_key,
                     enable_debug_info=enable_debug_info)
    return app