Fixing some tests and debugging others.

core/API/ResponseBuilder.php

core/DataTable/Filter/ComputeProcessedMetrics.php

core/DataTable/Filter/RemoveTemporaryMetrics.php

core/testMinimumPhpVersion.php

plugins/API/API.php

plugins/API/ProcessedReport.php

plugins/API/Reports/Get.php

plugins/VisitFrequency/Reports/Get.php

plugins/VisitsSummary/Reports/Get.php

tests/PHPUnit/Framework/TestRequest/Response.php

tests/PHPUnit/System/OneVisitorTwoVisitsTest.php

...HPUnit/System/TwoVisitorsTwoWebsitesDifferentDaysTest.php

...cted/test_OneVisitorTwoVisits__VisitFrequency.get_day.xml

.../expected/test_OneVisitorTwoVisits_csv__API.get_month.csv

..._differentDays_NotLastNPeriods__VisitsSummary.get_day.xml

...ifferentDays_NotLastNPeriods__VisitsSummary.get_month.xml

...ors_twoWebsites_differentDays__VisitFrequency.get_day.xml

...s_twoWebsites_differentDays__VisitFrequency.get_month.xml

...rs_twoWebsites_differentDays__VisitFrequency.get_week.xml

...rs_twoWebsites_differentDays__VisitFrequency.get_year.xml