Support html and wiki logbook entrys

Move nearest_station to nearest_station_name and make nearest_station a foreign
key to SurvexStation
Lots of tidying

templates/logbookentry.html

@@ -67,7 +67,12 @@
 <div id="col1">
   <div class="logbookentry">
     <b>{{logbookentry.date}}</b>
-    {{logbookentry.text}}</div>
+    {% if logbookentry.entry_type == "html" %}
+      <p>{{logbookentry.text|safe}}</p>
+    {% else %}
+      {{logbookentry.text|wiki_to_html}}
+    {% endif %}
+  </div>
 </div>
 </div>