Fix grouping of metrics with shared prefix

Naive sorting messes up the order of submetrics when they share a common
prefix. Providing a custom sort function makes sure that "longer" metric
names (without the submetric filter) are sorted after all submetrics of
the previous metric.

Example before:

    prefix...............: 1   414.40196/s
    prefix_suffix........: 1   414.40196/s
      { sub:two }........: 1   414.40196/s
      { sub:one }........: 1   414.40196/s

Example after:

    prefix...............: 1   414.40196/s
      { sub:one }........: 1   414.40196/s
    prefix_suffix........: 1   414.40196/s
      { sub:two }........: 1   414.40196/s

Closes grafana#2194

js/summary.js

@@ -299,7 +299,18 @@ function summarizeMetrics(options, data, decorate) {
     }
   })
 
-  names.sort()
+  // sort all metrics but keep sub metrics grouped with their parent metrics
+  names.sort(function (metric1, metric2) {
+    var parent1 = metric1.split('{', 1)[0]
+    var parent2 = metric2.split('{', 1)[0]
+    var result = parent1.localeCompare(parent2)
+    if (result !== 0) {
+      return result
+    }
+    var sub1 = metric1.substring(parent1.length)
+    var sub2 = metric2.substring(parent2.length)
+    return sub1.localeCompare(sub2)
+  })
 
   var getData = function (name) {
     if (trendCols.hasOwnProperty(name)) {