List of currencies is not retrieved on holidays

Today, the csv contains in the last column values of 'Bank holiday' and 'Not available'.

To account for these, the app now tries to select the column that makes more sense, going backwards day for day.

![Screenshot from 2013-03-30 07:38:03](https://f.cloud.github.com/assets/1790638/319986/79d4a5b2-9904-11e2-99ba-53b6c6be6fa6.png)