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

platform/android/dir_access_jandroid.cpp

@@ -29,7 +29,7 @@
 /*************************************************************************/
 
 #include "dir_access_jandroid.h"
-#include "core/print_string.h"
+#include "core/string/print_string.h"
 #include "file_access_jandroid.h"
 #include "string_android.h"
 #include "thread_jandroid.h"