Url structure

Here we remove all the hardcoding of urls, and put them into a nicer structure.

Removing the hardcoding means good use of `{% url %}` template tags, use of `django.core.urlresolvers.reverse_lazy` in login_required views.

Improving the structure means that login and logout now live at '/login/' and '/logout/', and that all the account info now live under the account app urlconfig, and are added to the root urlconfig through an include.