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

core/io/marshalls.cpp

@@ -30,9 +30,9 @@
 
 #include "marshalls.h"
 
+#include "core/object/reference.h"
 #include "core/os/keyboard.h"
-#include "core/print_string.h"
-#include "core/reference.h"
+#include "core/string/print_string.h"
 
 #include <limits.h>
 #include <stdio.h>