Support File Logging

[somefriggnidiot]

Story

As a bot owners
I want to save log messages to a file
So that I can review server activity at a later date.

Requirements

• Support is added for all existing logging messages to be able to be logged to a file.
• Message handler is updated to allow file logging.
• Config is updated to control granularity of file logging.
• Tests added/updated as applicable.
• Readme updated with example configuration and usage.

Design

A new logging file should be created for each day the bot is running (starting at system/environment 00:00), with each message on its own line.
Messages should use the same format and timestamp granularity as those logged to the console.

Technical Design

logToFile() method should be added to MessageHandler; should take care of actual logging of message.