Pretzel on azure arg

This PR contains a little more than I would like, but it is all related.

1. Command line args all cleaned up, now reports argument extensions properly (like vDir and now --azure) against the right command. Did this by extending the `IHaveCommandLineArgs` interface
1. Also made the help a bit nicer, see below
1. Introduced new interface `IAddtionalIngredient` which can be 'Mixed in' when creating the site. Tests added.

    starting pretzel...
    Usage:
    Pretzel.exe command [options]

          --help                 Display help mode
          --debug                Enable debugging

    Command: bake
      -t, --template=VALUE       The templating engine to use
      -d, --directory=VALUE      The path to site directory
      -p, --port=VALUE           The port to test the site locally
          --vDir=VALUE           Rewrite url's to work inside the specified
                                   virtual directory

    Command: import
      -i, --import=VALUE         The import type
      -f, --file=VALUE           Path to import file

    Command: create
      -t, --template=VALUE       The templating engine to use
      -d, --directory=VALUE      The path to site directory
          --azure                Enables deploy to azure support

    Command: taste
      -t, --template=VALUE       The templating engine to use
      -d, --directory=VALUE      The path to site directory
      -p, --port=VALUE           The port to test the site locally
          --nobrowser            Do not launch a browser
          --vDir=VALUE           Rewrite url's to work inside the specified
                                   virtual directory