updating changelog for the v3.18.1 release, [skip-ci]
updating changelog for the v3.18.1 release, [skip-ci]

ilios/ilios,dartajax/ilios,stopfstedt/ilios,dartajax/ilios,thecoolestguy/ilios,ilios/ilios,Trott/ilios,stopfstedt/ilios,thecoolestguy/ilios,Trott/ilios