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

servers/rendering/rasterizer.h

@@ -32,8 +32,8 @@
 #define RASTERIZER_H
 
 #include "core/math/camera_matrix.h"
-#include "core/pair.h"
-#include "core/self_list.h"
+#include "core/templates/pair.h"
+#include "core/templates/self_list.h"
 #include "servers/rendering_server.h"
 
 class RasterizerScene {