Instead of using an Arc Mutex for state management embedded directly
into the bot, utilize actor pattern, with the idea that this will be
much more useful than simply logging a message once in the future.
This also refactors the bot code so that instead of a single run_bot
function, the DiceBot struct now has a run() method attached to it.
This also necessitated changes and cleanup to the dicebot main, which
is for the better anyhow.
The error and config types are also now in their own files, and
implemented for more in-depth use cases.
