logging: Better colors

Inspired by https://github.com/borntyping/python-colorlog
INFO had no colors.
You can run weboob/tools/log.py to test them.
Proper English
Create a new logging level DEBUG_FILTERS

This is a cleaner approach that requires less configuration
in other applications.
This also easily allows us to have another color.

Many checks were made on being exactly at the DEBUG level, they were
fixed to also check on being below DEBUG (i.e. DEBUG_FILTERS).