An attempt to make diffing work the way I think it should

Basically, if a rom is a duplicate, it can be a duplicate within a system or source or across system or source, and by hash alone or by all data matching. The four combinations make an enum now and the diff function is the only one that uses them right now. If we're in dedup mode, we want to check hashes only in diff. Otherwise, we want to check against ones that match all information. This  needs field testing.

SabreHelper/Structs.cs

@@ -18,6 +18,6 @@
 		public string CRC;
 		public string MD5;
 		public string SHA1;
-		public bool Dupe;
+		public DupeType Dupe;
 	}
 }