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/pluginscript/pluginscript_script.h

@@ -32,7 +32,7 @@
 #define PLUGINSCRIPT_SCRIPT_H
 
 // Godot imports
-#include "core/script_language.h"
+#include "core/object/script_language.h"
 // PluginScript imports
 #include "pluginscript_language.h"
 #include <pluginscript/godot_pluginscript.h>