• Add CommandRegistrationCallback
• Add Client Command Api:
  • ClientCommandManager
  • ClientCommandSource

As soon as you approve the addition of the Item Group Api I will proceed with the implementation of my idea

CommandRegistrationCallback won't be necessary - 1.7.10 already has a command api.

On the other hand, a client command api would be an excellent addition. Ideally it should support both vanilla commands and sponge commands.

Now I'm going to do vanilla commands, tomorrow as soon as I pass the OGE I'll do the sponge version