clean up private fields/properties

GitOrigin-RevId: d2caf0d5d774e50ba4a2eb9cdc2a40ca28a094ce

Shared/Clock.cs

@@ -2,14 +2,12 @@
 
 namespace SemiColinGames {
   class Clock {
-    private static TimeSpan modelTime = new TimeSpan();
-
     public static void AddModelTime(double seconds) {
-      modelTime += TimeSpan.FromSeconds(seconds);
+      ModelTime += TimeSpan.FromSeconds(seconds);
     }
 
     public static TimeSpan ModelTime {
-      get { return modelTime; }
+      get; private set;
     }
   }
 }

Shared/World.cs

@@ -21,8 +21,8 @@ namespace SemiColinGames {
 
     public Tile(Texture2D texture, Terrain terrain, Rectangle position) {
       this.texture = texture;
-      this.Terrain = terrain;
-      this.Position = position;
+      Terrain = terrain;
+      Position = position;
     }
 
     public Rectangle Position { get; private set; }