Support saving version 1.6 archives

[victorbush]

Saving version 1.6 archives is not supported. As of now, I don't have a plan to support this.

My understanding of the 1.6 format is the archive data is stored in a .dat or .bin file, but the archive header is stored in the game executable itself. Modifying these archives would require either modifying the exe, or maybe doing some kind of runtime injection. Neither is trivial.