Error handling

[Zebiano]

I really dislike the way Voyager takes care of errors. For example checking if dbGuild has an error or not every time is annoying, There has to be a better way to treat any kind of error or exception or whatever. Like a general "Any and every error should be treated like the following" rule, but I doubt something like this exists.

Basically, take a look at all the errors that might occur while using the bot, and try to handle them in the best way possible.