Fixes bug with display of EU Decisions

This Pull Request fixes a bug with the display of Source and Term codes in the EU Decisions section of a Taxon Concept's page, see: http://www.speciesplus.net/#/taxon_concepts/5467/legal , output should be as the screenshot below:
![screen shot 2014-01-07 at 16 50 36](https://f.cloud.github.com/assets/10764/1860999/de573d06-77bb-11e3-9761-469aea710221.png)

- It also updates the distributions method in the show_taxon_concept serializer to use the variable name instead of name_en, for consistency.