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

gentest/gentest-cs.js

@@ -128,6 +128,9 @@ CSEmitter.prototype = Object.create(Emitter.prototype, {
 
   YGUndefined:{value:'YogaConstants.Undefined'},
 
+  YGDisplayFlex:{value:'YogaDisplay.Flex'},
+  YGDisplayNone:{value:'YogaDisplay.None'},
+
   YGWrapNoWrap:{value:'YogaWrap.NoWrap'},
   YGWrapWrap:{value:'YogaWrap.Wrap'},
 
@@ -176,6 +179,10 @@ CSEmitter.prototype = Object.create(Emitter.prototype, {
     this.push(nodeName + '.StyleDirection = ' + toValueCs(value) + ';');
   }},
 
+  YGNodeStyleSetDisplay:{value:function(nodeName, value) {
+    this.push(nodeName + '.Display = ' + toValueCs(value) + ';');
+  }},
+
   YGNodeStyleSetFlexBasis:{value:function(nodeName, value) {
     this.push(nodeName + '.FlexBasis = ' + toCsUnitValue(value) + ';');
   }},