Added FSO.Files for use with the API server

Don't ask me. FreeSO is the prime example of dependency hell.

server/tso.files/FAR3/FAR3Exception.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace FSO.Files.FAR3
+{
+    /// <summary>
+    /// Represents an exception thrown by a FAR3Archive instance.
+    /// </summary>
+    public class FAR3Exception : Exception
+    {
+        public FAR3Exception(string Message)
+            : base(Message)
+        {
+        }
+    }
+}