Added File Logging

Added :flex_logger and :logger_file_backend to enable logging to a file

Changed config from default to have two :flex_logger backends, :default_logger which logs to the console and :file_logger which logs to ./log/bot.log

If new applications are added that need logging in prod, they will need to be added in ./config/config.exs

The File Logger, in addition, includes the application, the module, and the function.

File logger will always be in debug mode. Console log will be in info mode, unless whitelisted

Closes #1 (closed)