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

editor/editor_file_dialog.cpp

@@ -33,7 +33,7 @@
 #include "core/os/file_access.h"
 #include "core/os/keyboard.h"
 #include "core/os/os.h"
-#include "core/print_string.h"
+#include "core/string/print_string.h"
 #include "dependency_editor.h"
 #include "editor_file_system.h"
 #include "editor_resource_preview.h"