Create custom commands using other commands

[AnidemDex]

I have the idea of creating custom commands that are made using other commands (CommandCollection on #58 can help here).

These custom collections will be displayed as a single command, but internally is a collection of n commands, following exactly the same behavior as normal commands.

Naturally, requirements for that probably implies:

• A way to design command block
• A way to define which properties are exposed and how