Start adding framework for separate filename

This will affect everything that outputs a DAT, there will be a new flag for inputting a filename (and reading and saving the filename in Parse).

SabreHelper/Data/Structs.cs

@@ -31,6 +31,7 @@ namespace SabreTools.Helper
 	public struct DatData
 	{
 		// Data common to most DAT types
+		public string FileName;
 		public string Name;
 		public string Description;
 		public string Category;