Implements #6820 Show System metric graphs on dashboard

interface/web/dashboard/dashboard.php

interface/web/dashboard/dashlets/metrics.php

interface/web/dashboard/dashlets/templates/metrics.htm

interface/web/dashboard/lib/lang/br_dashlet_metrics.lng

interface/web/dashboard/lib/lang/cn_dashlet_metrics.lng

interface/web/dashboard/lib/lang/de_dashlet_metrics.lng

interface/web/dashboard/lib/lang/en_dashlet_metrics.lng

interface/web/dashboard/lib/lang/es_dashlet_metrics.lng

interface/web/dashboard/lib/lang/fr_dashlet_metrics.lng

interface/web/dashboard/lib/lang/it_dashlet_metrics.lng

interface/web/dashboard/lib/lang/ja_dashlet_metrics.lng

interface/web/dashboard/lib/lang/nl_dashlet_metrics.lng

interface/web/dashboard/lib/lang/pl_dashlet_metrics.lng

interface/web/dashboard/lib/lang/ru_dashlet_metrics.lng

interface/web/js/chartjs/chart.cjs

interface/web/js/chartjs/chart.cjs.map

interface/web/js/chartjs/chart.js

interface/web/js/chartjs/chart.js.map

interface/web/js/chartjs/chart.umd.js

interface/web/js/chartjs/chart.umd.js.map