Reorganized core/ directory, it was too fatty already

-Removed FuncRef, since Callable makes it obsolete
-Removed int_types.h as its obsolete in c++11+
-Changed color names code

modules/gdnative/gdnative/vector2.cpp

@@ -31,7 +31,7 @@
 #include "gdnative/vector2.h"
 
 #include "core/math/vector2.h"
-#include "core/variant.h"
+#include "core/variant/variant.h"
 
 #ifdef __cplusplus
 extern "C" {