Add player and board size meta data to all game maps (#84)

* WIP: initial data model for new meta props
* WIP: implemented new props
* test and bug fix:
- add coverage of players and sizes
- fix unlimited map size bug
* FIX: update supported players for arcade to 6
* fix: test should be min -> max, not max->max
* Change some naming and the FixedSizes function
* update comment to reflect API changes
* improve comment clarity
* rename field for improved clarity
* change some more "map" -> "board" wording

maps/arcade_maze.go

@@ -20,6 +20,9 @@ func (m ArcadeMazeMap) Meta() Metadata {
 		Description: "Generic arcade maze map with deadly hazard walls.",
 		Author:      "Battlesnake",
 		Version:     1,
+		MinPlayers:  1,
+		MaxPlayers:  6,
+		BoardSizes:  FixedSizes(Dimensions{19, 21}),
 	}
 }