Have a more natural way to define Variant display values

[jkomoros]

Noticed while fixing #678 .

Variants are pretty heavy weight, especially around configuring the key/value displayName and description. It uses a heavyweight callback to fetch names and display names for each one. Originally I think that was to make it easy to get it added without having to write a lot of extra methods ;you could layer in the name/displayName/description later. also, that way you didn' tneed yet another silly top-level struct.

But in practice you always need to add that information for a real game, and things like #687 might help generate those methods for you automatically when you need them.

It might be that the name/displayName/description triple is useful for other things in the library so it doesn't have to be that big of a deal to add.

type VariantConfig []VariantKey

type VariantKey struct {
  Info VariantValue
  //The name of the value that is default
  Default string
  Values []VariantValue
}

//TODO: name this something more general?
type VariantValue struct {
  Name string
  DisplayName string
  Description string
}

func (g *gameDelegate) Variants() VariantConfig {
  return VarianConfig{
    Info: {
      Name: "size",
      DisplayName: "Size",
      Description: "Number of cards to use",
    },
    Default: "normal",
    Values: []VariantValue{
      {
        Name: "small",
        DisplayName: "Small",
        Description: "10 cards",
      },
      {
        Name: "normal",
        DisplayName: "Normal",
        Description: "100 cards",
      },
    },
  }
}

func (v VariantConfig) Valid() error {
  //Ensures deafult denotes one of the items (if not specified defaults to first), also verifies each key is unique name. If a Value is missing a DisplayName, the DisplayName defaults to title case of the Name, with "-" and "_" replaced with " ". (That could be a getter on VariantValue)
}

The config passed to your LegalVariant will have had any keys that aren't set set to their default.

[jkomoros]

• [ ] ensure stub output fits this pattern
• [ ] update TUTORIAL.md

[jkomoros]

Currently in progress on MBP

[jkomoros]

Actually this caused an infinite loop in memory game. BeginSetUp in memory is being passed an empty variant somehow.