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

javascript/sources/Node.hh

@@ -67,6 +67,7 @@ class Node {
     void setMarginPercent(int edge, double margin);
 
     void setOverflow(int overflow);
+    void setDisplay(int display);
 
     void setFlex(double flex);
     void setFlexBasis(double flexBasis);
@@ -111,6 +112,7 @@ class Node {
     Value getMargin(int edge) const;
 
     int getOverflow(void) const;
+    int getDisplay(void) const;
 
     Value getFlexBasis(void) const;
     double getFlexGrow(void) const;