Rewrite sequence loading logic.

Multiple layers of Lazy<T>ness are replaced with
an explicit two-part loading scheme.

Sequences are parsed immediately, without the need
for the sprite assets, and tell the SpriteCache
which frames they need. Use-cases that want the
actual sprites can then tell the SpriteCache to
load the frames and the sequences to resolve the
sprites.

OpenRA.Game/Map/MapPreview.cs

@@ -226,7 +226,7 @@ namespace OpenRA
 		{
 			return Ruleset.Load(modData, this, TileSet, innerData.RuleDefinitions,
 				innerData.WeaponDefinitions, innerData.VoiceDefinitions, innerData.NotificationDefinitions,
-				innerData.MusicDefinitions, innerData.SequenceDefinitions, innerData.ModelSequenceDefinitions);
+				innerData.MusicDefinitions, innerData.ModelSequenceDefinitions);
 		}
 
 		public MapPreview(ModData modData, string uid, MapGridType gridType, MapCache cache)