Breadcrumbs for nicer navigation [fixed PR]

Just like #59, but this time I didn't mess up my repository.

To recap:

* `breadcrumbs*` Django template tags are based on [Andriy Drozdyuk](http://drozdyuk.blogspot.com/2009/02/dagood-django-breadcrumbs.html) work, but I modified his code
* in update views there's now breadcrumb that links back to the object being edited