Support for mutliple input and output files

[nukeop]

Support needs to be added for encoding larger files in many carrier files. Currently the program aborts if the carrier file is too small to contain the secret data.

A virtual pseudo-filesystem can also be implemented when using multiple files. An encrypted header will store information about files, their sizes, and their locations. Any user with the key can then examine the contents of the filesystem which would be implemented on top of the existing steganographic functionality, like a big archive file encoded in multiple images.