Separate output streams for UI and logging

[konste]

Currently, UI and logging are mixed up together in a single stdout stream. This makes both (UI and logging) barely usable as they obscure each other.
I'd like to see the logs to be sent to the dedicated and configurable config file(s) (possibly with the size limitation, rotation and such) while UI output (which is not supposed to be huge) can go to stdout or GUI. If it goes to console it would be nice to use "curses" like Bazel does to keep the amount of output observable, but that would be a cherry on the cake, of course.