Multi-server support

[smileyhead]

Might have to look into sharding for this one.

List of changes that would need to be made (that I can think of, off the top of my head):

• quotes.json needs to be per-server – an appropriate new filename could be [server_id]-quotes.json.
  • Every quote command needs to pull from the appropriate database for the server.
• /exchange: The auto-complete currency list as well as the ‘Quick Reference’ Command are personalised for the currencies active people are familiar with in Mech's server. Alternative lists need to be created for each server the bot is on.
  • It would be better if a text command for customising the per-server currencies list was created, so that changes to currencies can be easily made.