Added proper cmd logging

changed all print statements in train.py and proloaf/ with logging statements. Added logging configuration file in json format. Logs can either be printed in the commandline or be logged in a .log file. Log settings can be adjusted for each module individually in the config file. The log level determines what the lowest level is, up from which logs are created

@florian.oppermann I added a logging function to the .cli package and added lines in every python file to create a logger. Please check if we should keep the functions in the .cli package or if they make more sense somewhere else.

Signed-off-by: Tobias Körner tobias.koerner@rwth-aachen.de

Closes #91