Brief overview of PR changes/additions

This PR is designed to let one generate paths to an object's web interface(s) from within a Django template.

It adds a set of methods to retrieve HTTP paths for DefaultAccount objects and all children of DefaultObject:

• get_admin_url(): Returns a path that, if followed, will display the object in the Admin backend.
• get_absolute_url(): Django construct; returns a path that should display the object in a DetailView.
• get_update_url(): Returns a path that should display the object in an UpdateView.
• get_delete_url(): Returns a path that should display the object in a DeleteView.

Note that this does not magically expose all your objects, create DeleteViews for everything, let random users into Admin or enable any sort of new or scary functionality.

The admin function works out of the box. It lets you do things in templates like:

{% if request.user.is_staff %}
<a href="{{ object.get_admin_url }}">Admin</a>
{% endif %}

...so when looking at an object (say, on a DetailView) staff can quickly pivot to the Admin backend to change things.

For the rest to work, you need to have defined named URLs that map typeclasses to actions. It must follow a particular naming convention (object-action, so account-update, character-delete or room-detail would yield the link to an appropriate view).

    # Character management
    url(r'^characters/create/$', website_views.CharacterCreateView.as_view(), name="character-create"),
    url(r'^characters/manage/$', website_views.CharacterManageView.as_view(), name="character-manage"),
    url(r'^characters/update/(?P<slug>[\w\d\-]+)/(?P<pk>[0-9]+)/$', website_views.CharacterUpdateView.as_view(), name="character-update"),
    url(r'^characters/delete/(?P<slug>[\w\d\-]+)/(?P<pk>[0-9]+)/$', website_views.CharacterDeleteView.as_view(), name="character-delete"),

This enables template functionality like:

{% for character in characters %}
<li>{{ character }} 
    <a href="{{ character.get_absolute_url }}">View</a> 
    <a href="{{ character.get_update_url }}">Update</a> 
    <a href="{{ character.get_delete_url }}">Delete</a>
</li>
{% endfor %}

...to let developers quickly generate links to the appropriate views governing disposition of an object. Securing those views and restricting access is entirely the responsibility of the developer; this PR does not facilitate anything that isn't already possible, just makes things more convenient for frontend development.

This PR also makes it more difficult to enumerate predictable endpoints (/accounts/1/, /accounts/2/, etc.). Evennia doesn't do slugs natively, though Django heavily encourages their use. When the link is generated, it passes the object pk as well as the slugified object name as kwargs. This means that the corresponding view must also be configured to receive and check an arbitrary slug kwarg, which is not the case by default. The receiving view should retrieve the object by pk but confirm the slug relates to the object name. This will inhibit scrapers and crawlers from probing random object IDs by requiring knowledge of both the object ID and the slugified version of the object name to be supplied to the view. It also makes the URL more intelligible (/accounts/johnny/1/, /accounts/frank/2/, etc.).