Made the configuration more flexible

- Allow individual asset files to be copied (in addition to a default
  folder).
- Let the user specify the favicon.ico in the html via:
    <link rel="icon" href="/public/favicon.ico" type="image/x-icon">
    <link rel="shortcut icon" href="/public/favicon.ico" type="image/x-icon">
  or something equivalent.
- Let the user specify the base URL and serve URL separately.