[SabreTools, DatFIle] Add base replacement

In this new update mode, a set of base DATs can be used as a replacement naming scheme for the input DATs. Only the item names will be updated, so this willl not fill in additional hashes or the like.

SabreTools.Library/Data/Flags.cs

@@ -240,6 +240,9 @@ namespace SabreTools.Library.Data
 
 		// Base diffs
 		Against = ReverseCascade << 1,
+
+		// Not technically diffs
+		BaseReplace = Against << 1,
 	}
 
 	/// <summary>