initial refactor of device export so it can be reused for future exporting

Disco.Models/Exporting/ExportResult.cs

@@ -0,0 +1,12 @@
+using System.IO;
+
+namespace Disco.Models.Services.Exporting
+{
+    public class ExportResult
+    {
+        public MemoryStream Result { get; set; }
+        public string Filename { get; set; }
+        public string MimeType { get; set; }
+        public int RecordCount { get; set; }
+    }
+}