Semantic MediaWiki 3.1.6

Released on April 19, 2020.

Bug fixes and internal code changes

#4648 as e8c9994: Makes "justinrainbow/json-schema" a hard requirement allowing for json-schema validation
#4667 as be7c3f4: Changes styling of the tables generated by the #smwdoc parser function
#4670 as e5c7417: Makes maintenance scripts compliant with psr-4 autoloading standard to avoid deprecation notices for Composer
93ac2b0 and 56f3e94: Fixes desc ordering of subjects for the "Datatables" result format