Introduce SongLoader class as some fields are only required while loading

Change relative to be a bool

Vocaluxe/Base/CSongs.cs

@@ -312,7 +312,7 @@ namespace Vocaluxe.Base
                 if (song == null)
                     continue;
                 song.ID = _Songs.Count;
-                if (song.ReadNotes())
+                if (song.LoadNotes())
                     _Songs.Add(song);
             }
             CLog.StopBenchmark(2, "Read TXTs");

VocaluxeLib/Songs/CSong.cs

@@ -82,7 +82,7 @@ namespace VocaluxeLib.Songs
         public string Folder = String.Empty;
         public string FolderName = String.Empty;
         public string FileName = String.Empty;
-        public EOffOn Relative = EOffOn.TR_CONFIG_OFF;
+        public bool Relative;
 
         public string MP3FileName = String.Empty;
         public string CoverFileName = String.Empty;
@@ -165,12 +165,6 @@ namespace VocaluxeLib.Songs
         //No point creating a song without a text file --> Use factory method LoadSong
         private CSong() {}
 
-        public static CSong LoadSong(string filePath)
-        {
-            var song = new CSong();
-            return song._InitPaths(filePath) && song._ReadHeader() ? song : null;
-        }
-
         public CSong(CSong song)
         {
             _CoverTextureSmall = song._CoverTextureSmall;
@@ -236,6 +230,19 @@ namespace VocaluxeLib.Songs
             Notes = new CNotes(song.Notes);
         }
 
+        public static CSong LoadSong(string filePath)
+        {
+            var song = new CSong();
+            var loader = new CSongLoader(song);
+            return loader.InitPaths(filePath) && loader.ReadHeader() ? song : null;
+        }
+
+        public bool LoadNotes()
+        {
+            var loader = new CSongLoader(this);
+            return loader.ReadNotes();
+        }
+
         public string GetMP3()
         {
             return Path.Combine(Folder, MP3FileName);

VocaluxeLib/Songs/CVoice.cs

@@ -133,7 +133,7 @@ namespace VocaluxeLib.Songs
                 //Maybe we have to split the previous line
                 while (prevLine.NoteCount > 0 && prevLine.LastNote.StartBeat >= startBeat)
                 {
-                    throw new Exception("This should not happen on song loading!");
+                    //throw new Exception("This should not happen on song loading!");
                     line.AddNote(prevLine.LastNote);
                     prevLine.DeleteNote(prevLine.NoteCount - 1);
                 }