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/websocket/websocket_client.h

@@ -32,7 +32,7 @@
 #define WEBSOCKET_CLIENT_H
 
 #include "core/crypto/crypto.h"
-#include "core/error_list.h"
+#include "core/error/error_list.h"
 #include "websocket_multiplayer_peer.h"
 #include "websocket_peer.h"