Show trip total distance on trip list page

Closes: #142

templates/trip_list.html

@@ -52,6 +52,7 @@
     <div class="heading"><h2>{{ heading }}</h2></div>
     <p>{{ items | count }} trips</p>
     {% for trip in items %}
+      {% set total_distance = trip.total_distance() %}
       {% set end = trip.end %}
       <div class="border border-2 rounded mb-2 p-2">
         <h3>
@@ -63,6 +64,11 @@
         {% else %}
           <div>Start: {{ display_date_no_year(trip.start) }} (end date missing)</div>
         {% endif %}
+        {% if total_distance %}
+          <div>Total distance:
+          {{ "{:,.0f} km / {:,.0f} miles".format(total_distance, total_distance / 1.60934) }}
+          </div>
+        {% endif %}
         <div class="conferences">
         {% for conf in trip.conferences %}
           {{ conference_row(conf, "going") }}