- add SimpleLogger class
- add LogLevel enum and current_log_level which serve to show only logs with level > to it
- add trace, debug, info, warning, error functions and their abbreviate form
- add _print function which is in charge to print the message
- the message can have timestamp and type being showed before the message [<type> ][<timestamp>]: <message>
- add the possibility to let specify a file where to save the file in append mode
