Added property display: flex and none

Summary:
Fix #241 and successor for #302

Added new property ```display``` with ```YGDisplayFlex``` and ```YGDisplayNone```. Allows to hide nodes from the layout without the need to remove it from the DOM.
Closes https://github.com/facebook/yoga/pull/369

Reviewed By: astreet

Differential Revision: D4501141

Pulled By: emilsjolander

fbshipit-source-id: 0dfeee381f6d1e4bbba81926126b83dd7abab9d6

csharp/Facebook.Yoga/YogaNode.cs

@@ -145,6 +145,19 @@ namespace Facebook.Yoga
             }
         }
 
+        public YogaDisplay Display
+        {
+            get
+            {
+                return Native.YGNodeStyleGetDisplay(_ygNode);
+            }
+
+            set
+            {
+                Native.YGNodeStyleSetDisplay(_ygNode, value);
+            }
+        }
+
         public YogaAlign AlignItems
         {
             get