Implement logging to file

[alex-eg]

While working on #19, I found myself in a dire need of logging facility.

I was debugging filter/list issue, and ncurses are not very friendly towards output that bypasses their own methods.

So I naturally did something like this:

with open("debug.log", "w") as f:
    ...
    print("List:", l, file=f)
    ...
    print("More info", info, file=f)

And so on. It was quite useful, but it's tedious to write this all by hand, and even more tedious to clean it all up. So I thought that we might benefit from having our own logging facility. In fact, I'm surprised that we don't have one yet.

UPD. It turned out we have logging after all. It's in utils.py. Whatever, then we need to have a wiki article on it.

[pkulev]

Logging in utils.py is bad implemented (not correctly configured root logger). There is issue about proper using of logging.

[pkulev]

Duplicates #27