Hide groups if all alerts within are silenced

Currently, even if all alerts within a group are silenced, the group
summary still appears. This can take up a lot of space when many alerts
are silenced.

If all alerts in a group are silenced and 'Hide silences' is checked,
hide the empty group.

bindata was updated by running:

    make assets format

template/internal/deftmpl/bindata.go

@@ -83,7 +83,7 @@ func templateDefaultTmpl() (*asset, error) {
 		return nil, err
 	}
 
-	info := bindataFileInfo{name: "template/default.tmpl", size: 16200, mode: os.FileMode(420), modTime: time.Unix(1469559122, 0)}
+	info := bindataFileInfo{name: "template/default.tmpl", size: 16200, mode: os.FileMode(420), modTime: time.Unix(1469708853, 0)}
 	a := &asset{bytes: bytes, info: info}
 	return a, nil
 }

ui/app/js/app.js

@@ -184,14 +184,18 @@ angular.module('am.controllers').controller('AlertsCtrl',
     });
 
     $scope.notEmpty = function(group) {
-      var l = 0;
+      var ret = false
+
       angular.forEach(group.blocks, function(blk) {
         if (this.indexOf(blk.routeOpts.receiver) >= 0) {
-          l += blk.alerts.length || 0;
+          var unsilencedAlerts = blk.alerts.filter(function (a) { return !a.silenced; });
+          if (!$scope.hideSilenced && blk.alerts.length > 0 || $scope.hideSilenced && unsilencedAlerts.length > 0) {
+            ret = true
+          }
         }
       }, $scope.receivers);
 
-      return l > 0;
+      return ret;
     };
 
     $scope.refresh = function() {