Add start offset settings.

Assets/Cryville/Crtr/ChartPlayer.cs

@@ -483,8 +483,9 @@ namespace Cryville.Crtr {
 					Game.MainLogger.Enumerate((level, module, msg) => { });
 					logs.text = "";
 				}
+				Game.AudioSequencer.SeekTime(startOffset, SeekOrigin.Current);
 				Game.AudioSequencer.Playing = true;
-				atime0 = Game.AudioClient.BufferPosition;
+				atime0 = Game.AudioClient.BufferPosition - startOffset;
 				inputProxy.SyncTime(cbus.Time);
 				started = true;
 			}

Assets/Cryville/Crtr/Settings.cs

@@ -164,7 +164,6 @@ namespace Cryville.Crtr {
 			}
 		}
 
-		[Browsable(false)]
 		[Category("debug")]
 		[Range(0, float.PositiveInfinity)][Step(10f)][Precision(1e-1)]
 		public float StartOffset {