Horrible bug here but only when there is more than one survex block per day, e.g. see Wookey 1999 where there are 3 eiscream survex blocks on 5th August. it duplicates the entry but gets it wrong. The length from the first block is displayed twice but there should be 3 rows: eiscream, eiscream2, eiscream3.

Fortunately it is just this display on this page which is wrong: no bad calculations get into the database.

The interaction of django database query idioms with django HTML templating language is a bit impenetrable here.
- The template is in troggle/templates/personexpedition.html
- The code is in function personexpedition() which calls GetPersonChronology() in troggle/core/views_logbooks.py
- the connection between the two is made in the URL resolver in troggle/urls.py

To be fixed!