Concurrent Streams per Day Graph (#2046)

* initial commit

* fix grouping in webserve

* remove event handler and adapt cursor

* optimize most concurrent calculation

* update branch from nightly and user filter

* max concurrent streams in graph

* made several changes mentioned in review

data/interfaces/default/js/graphs/concurrent_streams_by_stream_type.js

@@ -0,0 +1,76 @@
+var formatter_function = function() {
+    if (moment(this.x, 'X').isValid() && (this.x > 946684800)) {
+        var s = '<b>'+ moment(this.x).format('ddd MMM D') +'</b>';
+    } else {
+        var s = '<b>'+ this.x +'</b>';
+    }
+    $.each(this.points, function(i, point) {
+        s += '<br/>'+point.series.name+': '+point.y;
+    });
+    return s;
+};
+
+var hc_concurrent_streams_by_stream_type_options = {
+    chart: {
+        type: 'line',
+        backgroundColor: 'rgba(0,0,0,0)',
+        renderTo: 'graph_concurrent_streams_by_stream_type'
+    },
+    title: {
+        text: ''
+    },
+    legend: {
+        enabled: true,
+        itemStyle: {
+            font: '9pt "Open Sans", sans-serif',
+            color: '#A0A0A0'
+        },
+        itemHoverStyle: {
+            color: '#FFF'
+        },
+        itemHiddenStyle: {
+            color: '#444'
+        }
+    },
+    credits: {
+        enabled: false
+    },
+    plotOptions: {
+        series: {
+            events: {
+                legendItemClick: function() {
+                    setGraphVisibility(this.chart.renderTo.id, this.chart.series, this.name);
+                }
+            }
+        }
+    },
+    xAxis: {
+            type: 'datetime',
+            labels: {
+                formatter: function() {
+                    return moment(this.value).format("MMM D");
+                },
+                style: {
+                    color: '#aaa'
+                }
+            },
+            categories: [{}],
+            plotBands: []
+    },
+    yAxis: {
+            title: {
+                text: null
+            },
+            labels: {
+                style: {
+                    color: '#aaa'
+                }
+            }
+    },
+    tooltip: {
+        shared: true,
+        crosshairs: true,
+        formatter: formatter_function
+    },
+    series: [{}]
+};