Simplify config usage

[pkulev]

Now configs are read only, no need to create machinery to mantain wierd cases.
Now config (Settings) creates on import time, with some singletones raises problem of depending on import order.

Solution:

• make separate module common
• move all config related code from common.py to config.py
• create config not on reading time, use class or function
• look at singletones, maybe no need to use this antipattern