Enhanced Cooldown system

[Khaaz]

More customisation for cooldown.
Ability to use one or many of these CD types:

• Channel cd
• User cd
• Member cd
• Guild cd
  ...?
  CD should be coordinated by a CommandCooldown manager class, that will call ChannelCooldown, UserCooldown, MemberCooldown, GuildCooldown.
  This should be done using correct hierarchy and extension.