Add description for map when the game start

Plop,

I suggest that map editor can add a description in the start of a game when the map is used. Same when intruction are added in scenario.

Because, for example, to explain the context of the map, to explain how a map can be used (if we have mountains, we can say : "you can't go to mountains", or if it's a naval game etc.....)

I think, just allow to map to have instruction in the start. Because now, it's just scenario. Or, i don't know the method.