Logging an object's internal state

[jimc101]

To assist with debugging, it would be helpful if it was possible to log the internal state of an object. This could be done through a new method which writes the value of class member variables to a log file (e.g. using the logging package). Similar functionality could also be implemented in each object's __init__ method; however, this would be more difficult to control. If done using a new method, a series of log calls could be made from the run method in objects of type Simulator. log_level could be used to control if this information is recorded or not.