Logger: Stop using Log.File and Log.Level from config

This is a required step towards getting rid of ConfigurationTable class
and libsqlite dependency.

As a side effect, support for different log levels for different files
is dropped, but it's not something really being used and we will end up
dropping current logging system in favour of osmocom's one in the future
anyway.

Change-Id: I51cb12d1ab7e103e78190ac71a70fb5bb1d9ff51
2 files changed