Better CommandHandler

[Zelaux]

Added:

1. possibility to use spaces in param names
2. possibility to write required params after optional
3. variadic params may not be at the end
4. better exceptions

Added Tests for params parser and splitter

[Anuken]

General comments:

• Is all this complexity really necessary? 4 extra files for command parsing...?
• Are these changes really necessary at all?
  • Spaces in param names is a minor convenience, yes.
  • Why? This is very confusing. As a comparison, programming languages don't support this in methods, and for good reason. (C#: Optional parameters must appear after all required parameters)
  • Why? This, again, seems confusing to use, and, again, is not allowed in modern programming languages. (C#: A params parameter must be the last parameter in a formal parameter list)
• Formatting is completely off. See Mindustry's CONTRIBUTING.md.
  • You're adding spaces before braces.
  • SCREAMING_SNAKE_CASE should not be used.
  • Use wildcard imports.

[Zelaux]

1. All these 4 classes can be placed in one CommandHandler, but then it will turn into garbage
2. Example command /rate [player...] <score> by default player is my self, or other person, or server
   It's like overloding functions
3. Fixed

[Anuken]

2. Sure, but there's a trivial workaround: just put [player...] at the end. I don't think it's worth massive command handler changes just so a parameter can be reordered.

[Zelaux]

It seems to me from the point of view of use it is more logical to write like this
/rate [player...] <score>
it is more logical to first write who I want to rate
But if a want, I can just write a score

Another command
/pay <player...> <coins amount>

[Zelaux]

Also I guess my parser and splitter creates less strings