add logging functionality (#32)

[hackl]

Add functionality to log events in the console or in the .log file.

logger can be accessed via:

from pathpyG.utils.logger import logger
logger.info("Info Text")

or created by default logger module

import pathpyG as pp
import logging

logger = logging.getLogger("pathpyg")
logger.info("Info Text")

The default logger config is stored in the src pathpyG folder under logging.toml and can be replaced with a local logging.toml config in the working directory.