Introduce log file feature

[Sakthivel-Ramasamy]

Made code changes to capture and save all logs (from start to finish) generated from webex_bot library to a file with more data in the logs. Log enhancement is made to coloredLogs as well.

[Sakthivel-Ramasamy]

My tool was not able to pick up the webex_bot's log messages. I mapped my tool to use "webex_bot" logger created by webex_bot.py, but it missed out webex_websocket_client module's logs (from webex_websocket_client.py), as it was logging to its own logger created via logging.getLogger(__name__).

Also, even when I mapped my tool to use webex_bot's logger, it still missed out the initial log messages of webex_bot.py module.

With the code changes in this PR, all modules of webex_bot module will log to "webex_bot" logger and we can save the logs to a file, from the scratch.

Also, I have added code changes to trigger logger flush and close (via logging.shutdown()) when stop() is called.