Review use of PeopleGroups and JoshuaProject for population cross-references

[daniwelter]

The use of the above resources as cross-reference in AfPO has been flagged as problematic by some users at CZI, as both of these are religious resources aimed at identifying populations for proselytizing activities, and the language used in some of the PeopleGroups pages is particularly considered problematic. This brings into question the scientific validity of the information provided by these resources and whether including these cross-links in a scientific resource such as AfPO is a good idea.

If there is scientific merit to these cross-links, then this should be emphasised in the README. Otherwise these links should be removed/replaced as far as possible.