Create new branch. Goals: Make rocks size patches and frequency configruable. Optional but highly desired: Make rocks denser/more frequent the higher the altitude (make that an optional bool?)

Also the number display is screwed in the settings gui. Same problem as my other patch. Need to compare it to what I did for the other var I did recently (tiles width around rivers to make desert go away) and fix this. This will do to start with.

src/settings_type.h

@@ -375,6 +375,7 @@ struct GameCreationSettings {
 	byte   min_river_length;                 ///< the minimum river length
 	byte   river_route_random;               ///< the amount of randomicity for the route finding
 	byte   amount_of_rivers;                 ///< the amount of rivers
+	byte   amount_of_rocks;                  ///< the amoutn of rocks
 };
 
 /** Settings related to construction in-game */