Usability problem: update_file accepts very large files, and binary files

[Jacek Bzdak]

I made an error and instead of put_file used update_file for sending large 3GB gzipped file to server.

Whole Provy used about 12GB of RAM, but sent the file properly.

I guess we could issue an warning (error?) if someone uses this method to upload large binary file, as it does not make sense.

What do you think about it.