Refactor IMediaImage.Open to return error status instead of boolean.

Aaru.Images/AppleNIB/Read.cs

@@ -46,13 +46,13 @@ namespace Aaru.DiscImages
     public sealed partial class AppleNib
     {
         /// <inheritdoc />
-        public bool Open(IFilter imageFilter)
+        public ErrorNumber Open(IFilter imageFilter)
         {
             Stream stream = imageFilter.GetDataForkStream();
             stream.Seek(0, SeekOrigin.Begin);
 
             if(stream.Length < 512)
-                return false;
+                return ErrorNumber.InvalidArgument;
 
             byte[] buffer = new byte[stream.Length];
             stream.Read(buffer, 0, buffer.Length);
@@ -163,7 +163,7 @@ namespace Aaru.DiscImages
                     break;
             }
 
-            return true;
+            return ErrorNumber.NoError;
         }
 
         /// <inheritdoc />