routing: Simplify how routes are defined. * No more declaring the type of route parameters -- the sources and generators already know what type each parameter is supposed to be. * Same for variadic parameters -- we know already. * Update cache version to force a clear reload of the config. * Update tests. TODO: simplify code in the `Route` class to use source or generator transparently.

# This is a utility module that can be used with any WSGI-compatible server
# like Werkzeug or Gunicorn. It returns a WSGI app for serving a PieCrust
# website located in the current working directory.
import os
from piecrust.wsgiutil import get_app


root_dir = os.getcwd()
app = get_app(root_dir)
# Add this for `mod_wsgi`.
application = app