Add logging functionality

Description

As a user I would like to know more about the inner workings of icet and mchammer. A logging module already exists and is used in the fitting module. Using a logger has various advantages including the possibility to differentiate verbosity levels and redirection to file.

Tasks

  • setting up the logging framework
  • replace existing print statements (outside of print_* methods)

Comments

Demonstration

  • all tests pass
Edited by Paul Erhart