Resolves#2091.
This doesn't fix every OverflowError with MongoDB; but at least the seemingly easiest one to achieve with core cogs.
Signed-off-by: Toby Harradine <tobyharradine@gmail.com>
Allows cog creators to explain clearly why a cog cannot load by raising `redbot.core.errors.CogLoadError`. Instead of having to check in the console what's wrong, the message will directly be sent in the context channel.
