Add related places to place detail page (#1696)

[blms]

In this PR

Per #1696:

• Adapt Person.related_people into a new Place.related_places, which uses a subset of that functionality to get names and converse names of place-place relationships
• Show that on the Place Detail page using the styling and logic from Document Detail

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.95%. Comparing base (0a2c987) to head (8caaaa8).
Report is 4 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1730   +/-   ##
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  Coverage    98.95%   98.95%           
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  Files          247      247           
  Lines        16090    16133   +43     
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+ Hits         15922    15965   +43     
  Misses         168      168