Missing countries with duplicated adm0 SHPs

[t-downing]

Looks like the raster stats databases (or at least the seas5 one) is missing countries where the adm0 CODAB from FieldMaps has more than one polygon for adm0. From Confluence looks like this is BDI, NGA, and TCD (of which NGA and TCD we will be using alot).

Long term fix would be to manage the CODABs ourselves somehow, but short term maybe we could just filter the SHPs from FieldMaps. I know that for NGA and TCD it's the first row that's correct, but a more robust way to manage this would be to just take whichever one is bigger is a bigger polygon.

[hannahker]

@t-downing see #17 -- I've dissolved all the admin0 polygons here, since I noticed that some cases have non-overlapping admin 0 polygons.

[hannahker]

Closed with #17. @t-downing you should now find the raster stats for these ISO3s in the prod database.