CSV export for vendor search results and vendor detail page

Added CSV exports for the vendor search results and vendor detail page. These aren't linked anywhere yet because I knew the frontend was changing quite a bit. Here are some example links:

Search Results:
http://localhost:8000/pool/csv?naics-code=541330&setasides=A2,27

Vendor Detail:
http://localhost:8000/vendor/600985738/csv/
http://localhost:8000/vendor/600985738/csv/?naics-code=541330

I also updated the vendors fixture in the API folder. This was because quite a bit had changed in the vendors model so the fixture wouldn't load anymore and it made testing fail. 

Lastly, I updated the setaside fixture by adding a far_order attribute to the model and removing unused setasides.