Add option to pack/replace files as ID numbers instead of filenames

[RocketRobz]

There is a cpk file which contains files that have no filenames stored inside the cpk file, and instead, are stored as ID numbers.
As a result, when unpacking the files, they're shown as ID#####.
When repacking into a new cpk file, the files inside it are stored as filenames rather than ID numbers, and as a result, the game has trouble reading files inside the cpk file.

The game in question is Style Savvy: Styling Star (Nintendo 3DS), and the file I used is character_motion.cpk, which contain skeletal animations for the character models.

Download file here: https://www.dropbox.com/s/gqpagh7fa311fo7/character_motion.cpk?dl=1