Move configuration to new YGConfig and pass them down to CalculateLayout

Summary:
Move configuration to new ```YGConfig``` and pass them down to CalculateLayout. See #418 .

Adds ```YGConfigNew()``` + ```YGConfigFree```, and changed ```YGSetExperimentalFeatureEnabled``` to use the config.

New function for calculation is ```YGNodeCalculateLayoutWithConfig```.
Closes https://github.com/facebook/yoga/pull/432

Reviewed By: astreet

Differential Revision: D4611359

Pulled By: emilsjolander

fbshipit-source-id: a1332f0e1b21cec02129dd021ee57408449e10b0

javascript/sources/nbind.cc

@@ -13,6 +13,7 @@
 #include "./Layout.hh"
 #include "./Size.hh"
 #include "./Value.hh"
+#include "./Config.hh"
 #include "./global.hh"
 
 #define NBIND_DUPLICATE_POINTERS true
@@ -21,8 +22,6 @@
 
 NBIND_GLOBAL()
 {
-    function(setExperimentalFeatureEnabled);
-    function(isExperimentalFeatureEnabled);
     function(getInstanceCount);
 }
 
@@ -43,6 +42,13 @@ NBIND_CLASS(Value)
     construct<int, double>();
 }
 
+NBIND_CLASS(Config)
+{
+    method(create);
+    method(destroy);
+    method(setExperimentalFeatureEnabled);
+}
+
 NBIND_CLASS(Node)
 {
     method(create);