Use custom argument types for... custom argument types

[NorbiPeti]

Right now I'm using my own approach when it comes to custom command parameters (like plugins or components etc.). Brigadier has its own method which is to declare your own type. This probably can't be displayed on the client in any fancier way than before but it would make more sense to use it and report errors (using the same format as for primitive types) before the command execution logic even begins.