Restructure cookbook directories and use Grappelli for the admin interface.

Restructure cookbook directories and use Grappelli for the admin interface.

Moving the static and template directories into the python modules
makes it easy for Django to find them using its built-in finders:
  django.contrib.staticfiles.finders.AppDirectoriesFinder
  django.template.loaders.app_directories.Loader

This means that people using cookbook will not need to shift these
files around on their own, or adjust their settings.py file to do more
than add 'cookbook' to their INSTALLED_APPS.

Grappelli is makes it very easy to add drag-and-drop sorting for
Ingredient and IngredientBlock fields, which I also put in in this
commit.