choices: simple choose randomly from choices thing

similar to a hybrid of the random facts (but defined more simply) and
the dice rolling (but not picking from dice), this allows for definition
of "choice sets" (only in the admin for the moment) and then getting a
random pull from that set (only in the web interface for the moment)

dr_botzo/templates/base.html

@@ -72,6 +72,7 @@
         </div>
         {% block navbar_menu %}
           <ul class="nav navbar-nav">
+            <li><a href="{% url 'choices_index' %}">Choices</a></li>
             <li><a href="{% url 'karma_index' %}">Karma</a></li>
             <li><a href="{% url 'markov_index' %}">Markov</a></li>
             <li><a href="{% url 'races_index' %}">Races</a></li>