Add filename randomizing

[getimiskon]

I added some code that allows file randomization. Originally this code was added as a workaround to make files with filenames with non-Latin characters to be able to be uploaded. While that part is partially fixed, it's not finished yet, so this is the best way to handle these files for now.

[rfc-2549]

The message printed when your IP is banned is funny, and I won't change it.