[WebUI] Put total in the center of pie charts

interface/css/d3pie.css

     line-height: normal;
 }
 
+.d3pie .total-text {
+    text-anchor: middle;
+    dominant-baseline: central;
+}
+.d3pie .total-value {
+    font-family: Arial, sans-serif;
+}
+
 .d3pie .inner-label {
     fill: #eeeeee;
     pointer-events: none;

interface/css/rspamd.css

     text-align: left;
     font-size: 12px;
 }
-#rrd-pie {
-    font-size: 10px;
-}
 
 /* Throughput graph controls */
 #graph_controls select {

interface/js/app/graph.js

             size: {
                 canvasWidth: 400,
                 canvasHeight: 180,
+                pieInnerRadius: "50%",
                 pieOuterRadius: "80%"
             },
             labels: {
                     format: "none"
                 },
                 inner: {
-                    hideWhenLessThanPercentage: 8
+                    hideWhenLessThanPercentage: 8,
+                    offset: 0
                 },
             },
             padAngle: 0.02,
             pieCenterOffset: {
                 x: -120,
                 y: 10,
-            }
+            },
+            total: {
+                enabled: true
+            },
         };
 
         var ui = {};

interface/js/app/stats.js

             if (!graphs.chart) {
                 graphs.chart = new D3Pie("chart", {
                     labels: {
+                        inner: {
+                            offset: 0
+                        },
                         outer: {
                             collideHeight: 18,
                         }
                     },
-                    title: "Rspamd filter stats"
+                    size: {
+                        pieInnerRadius: "50%"
+                    },
+                    title: "Rspamd filter stats",
+                    total: {
+                        enabled: true,
+                        label: "Scanned"
+                    }
                 });
             }