Read receipt support & logging of self messages

[mitchcapper]

    Major additions to database driver (currently mysql only) to track metadata about messages.
    This currently allows us to support facebook read receipts on messages (will appear as eye emoji on the latest message they have seen)
    This also allows us to turn on self-events, this allows for logging into the slack channel messages sent by the facebook user on other devices.
    In the future this would allow for playing catch-up when disconnected from slack or facebook on a thread as we can figure out what messages we have or have not already taken care of.

This was a bit painful to do with all the code reformatting at the same time but 3rd rebase for the win:)

[mitchcapper]

If this is desired let me know and I will try to add pg support as well. For local file support would just not-support this for now.