default log level

This configuration values can be saved using:
	1. Default values inserted by developer		priority 0
	2. Configuration file					priority 1
	3. Passed as command line arguments	priority 2

Values with greater priority will overwrite values with less
priority.

Default value is overwritten by value in configuration file which
is overwritten by value passed on command line.

If no value was provided in configuration file or on command line
then the default value will be used.

Why this modification?
Imagine you define loglevel flag with value like "ERROR" ... when all flags will parsed, doesn't matter if you have passed a loglevel on command line, this variable will not be empty. In this situation, how to check if I need to overwrite the loglevel value defined in configuration file (which can be equal to "DEBUG")?

or maybe we don't need to think about putt the loglevel in configuration file?