rename SurvexScansFolders and tidy survex parser

templates/survexscansfolders.html

@@ -13,7 +13,7 @@ hand-drawn passage sections are drawn. These hand-drawn passages will eventually
 traced to produce Tunnel or Therion drawings and eventually the final complete cave survey.
 <table>
 <tr><th>Scans folder</th><th>Files</th><th>Survex blocks</th></tr>
-{% for survexscansfolder in survexscansfolders %}
+{% for survexscansfolder in manyscansfolders %}
   <tr>
     <td><a href="{{survexscansfolder.get_absolute_url}}">{{survexscansfolder.walletname}}</a></td>
     <td>{{survexscansfolder.survexscansingle_set.all|length}}</td>

templates/tunnelfiles.html

@@ -17,7 +17,7 @@
     <td>{{tunnelfile.npaths}}</td>   
 
     <td>
-    {% for survexscansfolder in tunnelfile.survexscansfolders.all %}
+    {% for survexscansfolder in tunnelfile.manyscansfolders.all %}
       <a href="{{survexscansfolder.get_absolute_url}}">{{survexscansfolder.walletname}}</a>
     {% endfor %}
     </td>