add PlayerPaletteFromCurrentTileset and desert tileset for RA

some things left to do:
ore, walls and silo/hbox need some work

OpenRA.FileFormats/Map/TileSet.cs

@@ -78,6 +78,7 @@ namespace OpenRA.FileFormats
 		public string Name;
 		public string Id;
 		public string Palette;
+		public string PlayerPalette;
 		public int TileSize = 24;
 		public string[] Extensions;
 		public int WaterPaletteRotationBase = 0x60;