perf(animation): improves _progress() hot function

- progress() is the function where more time is spent during any swipe gesture
- replace iterating over the _fx properties, using an array instead
- optimize pointerCoord(), profiler showed it’s one of the most called functions

src/components/menu/menu.scss

@@ -51,7 +51,7 @@ ion-menu ion-backdrop {
   z-index: -1;
   display: none;
 
-  opacity: .1;
+  opacity: .01;
 }
 
 .menu-content {

src/components/refresher/test/refresher.spec.ts

@@ -232,7 +232,8 @@ describe('Refresher', () => {
   function touchEv(y: number) {
     return {
       type: 'mockTouch',
-      touches: [{clientY: y}],
+      pageX: 0,
+      pageY: y,
       preventDefault: function(){}
     };
   }