Use ISO codes of countries to count site countries

[norkans7]

No description provided.

[codecov-io]

Codecov Report

Merging #645 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #645      +/-   ##
==========================================
+ Coverage   85.15%   85.16%   +0.01%     
==========================================
  Files          37       37              
  Lines        3948     3951       +3     
==========================================
+ Hits         3362     3365       +3     
  Misses        586      586              

Impacted Files	Coverage Δ
ureport/public/views.py	89.83% <100.00%> (+0.08%)	⬆️

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