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/cvtt/image_compress_cvtt.h

@@ -31,7 +31,7 @@
 #ifndef IMAGE_COMPRESS_CVTT_H
 #define IMAGE_COMPRESS_CVTT_H
 
-#include "core/image.h"
+#include "core/io/image.h"
 
 void image_compress_cvtt(Image *p_image, float p_lossy_quality, Image::UsedChannels p_channels);
 void image_decompress_cvtt(Image *p_image);