fix(touchInteractionEvents): fire dblClick with button=1

* fixes upstream bpmn-io/bpmn-js#618
* testing infrastructure is not set up here. Hence I am skipping the
  testing bit. We need to set up proper testing, when reworking the
entire touch module.
* manual integration test done with bpmn-js direct editing module and
  ipad safari

lib/features/touch/TouchInteractionEvents.js

@@ -149,15 +149,24 @@ export default function TouchInteractionEvents(
   // the touch recognizer
   var recognizer;
 
-  function handler(type) {
+  function handler(type, buttonType) {
 
     return function(event) {
       log('element', type, event);
 
-      interactionEvents.fire(type, event);
+      var gfx = getGfx(event.target),
+          element = gfx && elementRegistry.get(gfx);
+
+      // translate into an actual mouse click event
+      if (buttonType) {
+        event.srcEvent.button = buttonType;
+      }
+
+      return interactionEvents.fire(type, event, element);
     };
   }
 
+
   function getGfx(target) {
     var node = domClosest(target, 'svg, .djs-element', true);
     return node;
@@ -168,10 +177,6 @@ export default function TouchInteractionEvents(
     // touch recognizer
     recognizer = createTouchRecognizer(svg);
 
-    recognizer.on('doubletap', handler('element.dblclick'));
-
-    recognizer.on('tap', handler('element.click'));
-
     function startGrabCanvas(event) {
 
       log('canvas', 'grab start');
@@ -248,6 +253,9 @@ export default function TouchInteractionEvents(
       recognizer.on('pinchcancel', end);
     }
 
+    recognizer.on('tap', handler('element.click'));
+    recognizer.on('doubletap', handler('element.dblclick', 1));
+
     recognizer.on('panstart', startGrab);
     recognizer.on('press', startGrab);